BUG: np.round()/np.around() fails on Float64Index
Seems that it's looking for an attribute that's invalid.

```
print type(idx)
<class 'pandas.core.index.Float64Index'>
```

Where I created Float64Index elsewhere...

```
np.round(idx)
Traceback (most recent call last):
  File "/home/glue/Desktop/PYUVVIS/pyuvvis/pyuvvis/core/timespectra.py", line 1, in <module>
    """Provides core "TimeSpectra" class and associated utilities."""
  File "/home/glue/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/numpy/core/fromnumeric.py", line 2629, in round_
    return round(decimals, out)
AttributeError: rint
```
