BUG/VIS: rot and fontsize are not applied to timeseries plots
In some plots, `rot` and `fontsize` arguments are not applied properly.
- timeseries line / area plot: `rot` is not applied to minor ticklabels, and `fontsize` is completely ignored. (Fixed to apply to xticklabels)
- kde plot: `rot` and `fontsize` are completely ignored. (Fixed to apply to xticklabels)
- scatter and hexbin plots: `rot` and `fontsize` are completely ignored. (Under confirmation)

```
import pandas as pd
import numpy as np

df = pd.DataFrame(np.random.randn(10, 4), index=pd.date_range(start='2014-07-01', freq='M', periods=10))
df.plot(rot=80, fontsize=15)
```
### Current Result

![figure_ng](https://cloud.githubusercontent.com/assets/1696302/3709379/7841977e-1454-11e4-8396-fc42e943d54a.png)
### After Fix

![figure_ok](https://cloud.githubusercontent.com/assets/1696302/3709380/7cc1037a-1454-11e4-9456-a9335907473b.png)

The problem affects to kde, scatter, and hexbin plots. These all ignores `rot` and `fontsize` now.

In kde, I think it is natural to use `rot` and `fontsize` for `xticklabels`. But in `scatter` and `hexbin`, maybe better to apply to both `xticklabels` and `yticklabels`? Or only to `xticklabels`?
 @sinhrks thanks....
