BLD: 0 13 pickles
closes #4796

cc @TomAugspurger

can you generate a pickle on the mac for us?

pull down this branch, build like: 

```
python setup.py build

vagrant@precise32:~/0_13_pickles/build/lib.linux-i686-2.7$ python ../../pandas/io/tests/generate_legacy_pickles.py 0.13.0 ../../pandas/io/tests/data/legacy_pickle/0.13.0/
/usr/local/lib/python2.7/dist-packages/pytz-2013b-py2.7.egg/pytz/__init__.py:35: UserWarning: Module pandas was already imported from ./pandas/__init__.pyc, but /usr/local/lib/python2.7/dist-packages/pandas-0.12.0-py2.7-linux-i686.egg is being added to sys.path
  from pkg_resources import resource_stream
This script generates a pickle file for the current arch, system, and python version
  system version: 
  output version: 0.13.0
  output dir    : ../../pandas/io/tests/data/legacy_pickle/0.13.0/
created pickle file: 0.13.0_i686_linux_2.7.3.pickle
```

then commit and do a PR on this branch.....thanks
 Getting an import error.

```
 pandas-dev  tom  dhcp80fff527  ~  Envs  …  python2.7  site-packages  pandas  jreback-0_13_pickles  $ python pandas/io/tests/generate_legacy_pickles.py 0.13.0
Traceback (most recent call last):
  File "pandas/io/tests/generate_legacy_pickles.py", line 146, in <module>
    write_legacy_pickles()
  File "pandas/io/tests/generate_legacy_pickles.py", line 114, in write_legacy_pickles
    import pandas.util.testing as tm
  File "./pandas/util/testing.py", line 40, in <module>
    from pandas import _testing
ImportError: cannot import name _testing
```

I'll see what I can figure out.
 did you rebuild ? that was just added.....
 I had used `python setup.py develop` in that virtualenv previously. Doing `develop` this time worked.
 OK so I've pushed it [here](https://github.com/TomAugspurger/pandas/tree/jreback-0_13_pickles)

I want to PR against this PR right? I hope I did that correctly: https://github.com/jreback/pandas/pull/7
 @TomAugspurger thanks....everything working so far.....cross-fingers
 any one have a windows 3.3 build setup can can contribute a pickle?

any other relevant archs/combinations think are needed?
