Fixes to resample over DST boundaries
closes #5172 
closes #8744
closes #8653 
closes #9173
closes #9468
closes #8794

fixes all issues but one attached to #5172.  There were several issues as mentioned by my comments in the master list.  They are:
1. Offset classes were not working properly over DST boundaries.  I added flags on the class to handle specially.
2. `normalize_date` does not work with DST change dates as the tz offset is not adjusted. `normalize` is added to Timestamp as discussed in #8794 (I don't like how this was done, but it seemed the easiest rather than duplicating lots of code in `tslib.date_normalize`.
3. `_adjust_dates_anchored` was not localizing properly once times were adjusted. 

The outstanding issue is #9119 which is timezone related, but not DST related.
 @rockg awesome!

I listed all of the issues, pls give a check.

pls give a release note (listing all of the issues) as well.
 @rockg can you run a perf test (looks like it should be fine, but pls check)
 @rockg I'd like to get this in the 0.16.0 rc, which I am going to do prob tomorrow (0.16. prob 1 week later), can you update?
 Yes, fixing everything up.  Should have something in an hour.
 Wow that vbench takes over an hour (and it only works for python 2 which was a nice surprise).  There are a few date things in here which surprised me.

```
reshape_stack_simple                         |   3.8433 |   3.5164 |   1.0930 |
frame_ctor_dtindex_BusinessDayx1             |   2.2870 |   2.0920 |   1.0932 |
dataframe_resample_min_numpy                 |   3.2500 |   2.9697 |   1.0944 |
frame_ctor_dtindex_CustomBusinessDayx1       |   2.3030 |   2.1026 |   1.0953 |
frame_ctor_dtindex_BDayx2                    |   2.3340 |   2.1287 |   1.0965 |
frame_ctor_dtindex_YearBeginx1               |   2.2504 |   2.0523 |   1.0965 |
frame_ctor_dtindex_CBMonthEndx1              |   6.5024 |   5.8760 |   1.1066 |
groupby_ngroups_100_sum                      |   0.7041 |   0.6344 |   1.1099 |
groupby_ngroups_100_count                    |   0.5260 |   0.4703 |   1.1183 |
reshape_unstack_simple                       |   5.0033 |   4.4693 |   1.1195 |
concat_empty_frames2                         |   1.4807 |   1.3180 |   1.1234 |
timeseries_custom_bmonthend_incr             |   0.3620 |   0.3190 |   1.1348 |
panel_shift_minor                            |   0.1633 |   0.1436 |   1.1372 |
replace_replacena                            |   2.7843 |   2.4397 |   1.1413 |
timeseries_custom_bmonthbegin_decr_n         |   0.4679 |   0.4090 |   1.1442 |
replace_fillna                               |   3.4404 |   3.0044 |   1.1451 |
timeseries_iter_periodindex_preexit          |  14.1080 |  12.3093 |   1.1461 |
timeseries_custom_bmonthbegin_incr_n         |   0.4480 |   0.3854 |   1.1625 |
strings_lower                                |   5.3800 |   4.4383 |   1.2122 |
timeseries_custom_bday_cal_decr              |   0.0687 |   0.0520 |   1.3211 |
timeseries_custom_bday_decr                  |   0.0679 |   0.0513 |   1.3235 |
timeseries_custom_bday_cal_incr_neg_n        |   0.0690 |   0.0517 |   1.3354 |
timeseries_custom_bday_cal_incr              |   0.0617 |   0.0447 |   1.3808 |
timeseries_custom_bday_cal_incr_n            |   0.0620 |   0.0447 |   1.3879 |
timeseries_year_apply                        |   0.0453 |   0.0319 |   1.4179 |
timeseries_year_incr                         |   0.0490 |   0.0337 |   1.4528 |
timeseries_custom_bday_apply_dt64            |   0.0520 |   0.0356 |   1.4598 |
timeseries_custom_bday_incr                  |   0.0477 |   0.0320 |   1.4888 |
timeseries_custom_bday_apply                 |   0.0456 |   0.0306 |   1.4909 |
frame_object_equal                           |  21.1930 |  11.3687 |   1.8642 |
frame_nonunique_equal                        |  21.2193 |  11.3026 |   1.8774 |
```
 vbench looks fine, the things that take < 1ms are really hard to time correctly.
usually I pass `-r regex` which will only do those tests that are most interesting.
 Great news.
 I think this is ok, however, need to check one thing. Can you make a pickle from 0.15.2 and add to the tests, like this: https://github.com/pydata/pandas/blob/master/pandas/tests/test_categorical.py#L2640 (need to test that the DateOffsets survive this change). Basically save say a dict of a couple of examples, pickle it to a file (in 0.15.2), then read in (in the tests) and make sure they compare equal (I think they should), but since adding this attribute, need to make sure.
 The pickle test worked fine.  Think we should be good on that front.
 ok looks good

will merge in the morning

if u have s chance see if anything needs to be updated in the docs about tz (eg in resample section) 
 merged via https://github.com/pydata/pandas/commit/dcc68d7c5a06df85fe9fec568566bee1e9936b10

thanks!
 @jreback...thanks.  There are a couple travis errors on two of 2.7 jobs with the pickle test (however one of them succeeded).  Any thoughts? 

```
======================================================================
ERROR: test_pickle_v0_15_2 (pandas.tseries.tests.test_offsets.TestCommon)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/travis/build/pydata/pandas/pandas/tseries/tests/test_offsets.py", line 424, in test_pickle_v0_15_2
    self.assertEqual(offsets, read_pickle(pickle_path))
  File "/home/travis/build/pydata/pandas/pandas/io/pickle.py", line 60, in read_pickle
    return try_read(path)
  File "/home/travis/build/pydata/pandas/pandas/io/pickle.py", line 57, in try_read
    return pc.load(fh, encoding=encoding, compat=True)
  File "/home/travis/build/pydata/pandas/pandas/compat/pickle_compat.py", line 116, in load
    return up.load()
  File "/home/travis/miniconda/envs/pandas/lib/python2.6/pickle.py", line 858, in load
    dispatch[key](self)
  File "/home/travis/build/pydata/pandas/pandas/compat/pickle_compat.py", line 20, in load_reduce
    stack[-1] = func(*args)
  File "/home/travis/miniconda/envs/pandas/lib/python2.6/copy_reg.py", line 48, in _reconstructor
    obj = object.__new__(cls)
TypeError: object.__new__(X): X is not a type object (classobj)
```
 I rebuilt the pick on 0.15.2 and it works fine. How did you create the pickle?

I have only seen this error IIRC if you pickle I think in text mode.
 I thought I used the same recipe as your example.  I created a new
virtualenv and saved the pickle with the file in 'wb' mode.
 Python 2?
 Almost positive (I can confirm tonight).  I am positive that I ran the test locally with Python 2.7.  Anyways, I'm not sure it's worth more thought right now.  Thanks for taking care of it.
