Warning issued every time Pandas is imported
I am getting the following warning every time I import Pandas in any script

```
/usr/local/lib/python2.7/site-packages/matplotlib/__init__.py:872: UserWarning: axes.color_cycle is deprecated and replaced with axes.prop_cycle; please use the latter.
  warnings.warn(self.msg_depr % (key, alt_key))
```

One example would be

``` python
>>> import pandas
/usr/local/lib/python2.7/site-packages/matplotlib/__init__.py:872: UserWarning: axes.color_cycle is deprecated and replaced with axes.prop_cycle; please use the latter.
  warnings.warn(self.msg_depr % (key, alt_key))
```

I am running on OSX a "brewed" Python 2.7 with pandas==0.17.1 and matplotlib==1.5.0.

Thanks in advance
