BUG: Make Index, Int64Index and MI repr evalable
MI repr was missing a comma between its arguments and Index reprs needed
to quote their dtypes.

Only talking about Index, Int64Index and
MultiIndex. Tseries indices (like PeriodIndex and DatetimeIndex) are
more complicated and could be covered separately.

To be clear, the major change is to add commas between MI attributes and quote dtypes for Index. So, pre this PR:

``` python
repr(Index(range(10)))
Int64Index([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], dtype=int64)
```

With this PR

``` python
repr(Index(range(10)))
Int64Index([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], dtype='int64')
```

Everybody okay with that?
 ok with this
 Okay, I'll make sure it still passes and then push.
