Int64Index does not support modulo operator under pandas 0.15
In pandas 0.15, a DataFrame's index no longer supports the modulo operator.  I believe the following code used to work under pandas 0.14, but under pandas 0.15, a TypeError indicating "unsupported operand types" is raised:

```
In [1]: import pandas                                                                                                                                                                                                                        

In [2]: print pandas.version.version                                                                                                                                                                                                         
0.15.2

In [3]: df = pandas.DataFrame({ 'i': xrange(10) })                                                                                                                                                                                           

In [4]: df.index                                                                                                                                                                                                                             
Out[4]: Int64Index([0, 1, 2, 3, 4, 5, 6, 7, 8, 9], dtype='int64')

In [5]: r = df.index % 2                                                                                                                                                                                                                     
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-5-405b698d3a56> in <module>()
----> 1 r = df.index % 2

TypeError: unsupported operand type(s) for %: 'Int64Index' and 'int'

In [6]: r = df.index.to_series() % 2

In [7]: 
```

Line 6 shows that a workaround exists, using the to_series() function.

This issue is very similar to [Issue #8608](https://github.com/pydata/pandas/issues/8608), which dealt with other arithemtic operations on an index.  Pandas commit [2fcbc7f](https://github.com/pydata/pandas/pull/8634/commits) fixed that issue by adding addition, subtraction, multiplication, division, and unary operators, but not the modulo operator.
