MonthOffset() gives increase of 1 day instead of 1 month
From https://github.com/pydata/pandas/pull/7375#issuecomment-48465256:

```
In [67]: from pandas.tseries import offsets

In [69]: d = pd.Timestamp('2014-01-01 09:00:00')

In [70]: d + offsets.MonthOffset()
Out[70]: Timestamp('2014-01-02 09:00:00')

In [71]: offsets.MonthOffset().apply(d)
Out[71]: Timestamp('2014-01-02 09:00:00')

In [72]: d + offsets.Day()
Out[72]: Timestamp('2014-01-02 09:00:00')
```
