BLD/TST: matplotlib 1.2.1 issues
https://travis-ci.org/jreback/pandas/jobs/42570209

tests that need skipping on matplotlib 1.2.1

```
=====================================================================
ERROR: test_hist_df_coord (pandas.tests.test_graphics.TestDataFramePlots)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/travis/build/jreback/pandas/pandas/tests/test_graphics.py", line 2145, in test_hist_df_coord
    ax = df.plot(kind='hist', bins=5, orientation='horizontal')
  File "/home/travis/build/jreback/pandas/pandas/tools/plotting.py", line 2454, in plot_frame
    **kwds)
  File "/home/travis/build/jreback/pandas/pandas/tools/plotting.py", line 2294, in _plot
    plot_obj.generate()
  File "/home/travis/build/jreback/pandas/pandas/tools/plotting.py", line 920, in generate
    self._make_plot()
  File "/home/travis/build/jreback/pandas/pandas/tools/plotting.py", line 1949, in _make_plot
    artists = plotf(ax, y, column_num=i, **kwds)
  File "/home/travis/build/jreback/pandas/pandas/tools/plotting.py", line 1929, in plotf
    bottom=bottom, **kwds)
  File "/home/travis/miniconda/envs/pandas/lib/python2.7/site-packages/matplotlib/axes.py", line 8180, in hist
    color=c, bottom=bottom)
TypeError: barh() got multiple values for keyword argument 'bottom'
======================================================================
ERROR: test_hist_kwargs (pandas.tests.test_graphics.TestSeriesPlots)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/travis/build/jreback/pandas/pandas/tests/test_graphics.py", line 821, in test_hist_kwargs
    ax = self.ts.plot(kind='hist', orientation='horizontal')
  File "/home/travis/build/jreback/pandas/pandas/tools/plotting.py", line 2488, in plot_series
    **kwds)
  File "/home/travis/build/jreback/pandas/pandas/tools/plotting.py", line 2294, in _plot
    plot_obj.generate()
  File "/home/travis/build/jreback/pandas/pandas/tools/plotting.py", line 920, in generate
    self._make_plot()
  File "/home/travis/build/jreback/pandas/pandas/tools/plotting.py", line 1949, in _make_plot
    artists = plotf(ax, y, column_num=i, **kwds)
  File "/home/travis/build/jreback/pandas/pandas/tools/plotting.py", line 1929, in plotf
    bottom=bottom, **kwds)
  File "/home/travis/miniconda/envs/pandas/lib/python2.7/site-packages/matplotlib/axes.py", line 8180, in hist
    color=c, bottom=bottom)
TypeError: barh() got multiple values for keyword argument 'bottom'
----------------------------------------------------------------------
Ran 194 tests in 1178.119s
```
