ENH: Dropping outliers
Create a new function to remove outliers.

http://stackoverflow.com/questions/23199796/detect-and-exclude-outliers-in-pandas-dataframe

I find myself using the code from SO quite often to remove outliers in a particular column when preprocessing data and it seems this is a common issue. It would be nice to have a function that operates on a Series to do this automatically.

#### Code Sample, a copy-pastable example if possible

```python
df = pd.DataFrame(np.random.randn(100, 3))

# from SO answer by tanemaki
from scipy import stats
df[(np.abs(stats.zscore(df)) < 3).all(axis=1)]

# instead, would prefer
df.drop_outliers(3)

```

Alternatively, instead of a new function, we could modify .clip(), though I think a new function makes more sense.

The implementation could be similar to the SO implementation.

If there is agreement that this would be useful and the implementation makes sense, happy to do the PR.

