COMPAT: some compatibility fixes with new numpies
@tacaswell @mdboom, using mpl 1.5.0 here. I was turning on deprecation warnings. (we get a bunch of these in test suite), known issue?

cc @TomAugspurger 

```
======================================================================
ERROR: test_ts_area_lim (pandas.tests.test_graphics.TestSeriesPlots)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "pandas/tests/test_graphics.py", line 612, in test_ts_area_lim
    ax = self.ts.plot.area(stacked=False, x_compat=True)
  File "pandas/tools/plotting.py", line 3688, in area
    return self(kind='area', **kwds)
  File "pandas/tools/plotting.py", line 3564, in __call__
    **kwds)
  File "pandas/tools/plotting.py", line 2643, in plot_series
    **kwds)
  File "pandas/tools/plotting.py", line 2439, in _plot
    plot_obj.generate()
  File "pandas/tools/plotting.py", line 1032, in generate
    self._post_plot_logic_common(ax, self.data)
  File "pandas/tools/plotting.py", line 1160, in _post_plot_logic_common
    fontsize=self.fontsize)
  File "pandas/tools/plotting.py", line 1208, in _apply_axis_properties
    labels = axis.get_majorticklabels() + axis.get_minorticklabels()
  File "/Users/jreback/miniconda/lib/python2.7/site-packages/matplotlib/axis.py", line 1161, in get_majorticklabels
    ticks = self.get_major_ticks()
  File "/Users/jreback/miniconda/lib/python2.7/site-packages/matplotlib/axis.py", line 1290, in get_major_ticks
    numticks = len(self.get_major_locator()())
  File "/Users/jreback/miniconda/lib/python2.7/site-packages/matplotlib/dates.py", line 1007, in __call__
    return self._locator()
  File "/Users/jreback/miniconda/lib/python2.7/site-packages/matplotlib/dates.py", line 813, in __call__
    return self.tick_values(dmin, dmax)
  File "/Users/jreback/miniconda/lib/python2.7/site-packages/matplotlib/dates.py", line 830, in tick_values
    self.rule.set(dtstart=start, until=stop, count=self.MAXTICKS + 1)
  File "/Users/jreback/miniconda/lib/python2.7/site-packages/matplotlib/dates.py", line 724, in set
    self._rrule = rrule(**self._construct)
  File "/Users/jreback/miniconda/lib/python2.7/site-packages/dateutil/rrule.py", line 470, in __init__
    "raise an error.", DeprecationWarning)
DeprecationWarning: Using both 'count' and 'until' is inconsistent with RFC 2445 and has been deprecated in dateutil. Future versions will raise an error.
```
 Thanks for pointing out.  Not a known issue (to me at least).  I'll see if I can reproduce locally.
 @mdboom this is using pretty recently released `python-dateutil 2.5.3` FYI (might be new there)
 There is a pr fixing this, but I am failing to find it.
 https://github.com/matplotlib/matplotlib/issues/6155 / https://github.com/matplotlib/matplotlib/pull/6190
 Thanks @tacaswell.  Unfortunately, it doesn't look there's much of a way to workaround that from the outside...
 the fix will be it 1.5.2 / 2.0, which ever comes first
 thanks @mdboom @tacaswell no worries. just trying to have clean test outputs.
