re-evaluate axis types on read_csv(index_col=...)
``` python

In [71]: data = """\
   ....: this, that, 0, 1
   ....: 10, 20, 30, 40
   ....: 50, 60, 70, 80
   ....: """

In [72]: df  = pd.read_csv(StringIO(data), index_col=[0, 1])

In [73]: df
Out[73]: 
             0   1
this  that        
10   20     30  40
50   60     70  80

In [74]: df.index  # <-- ok  -->
Out[74]: 
MultiIndex
[(10L, 20L) (50L, 60L)]

In [75]: df.columns  # <-- Int64 can be used -->>
Out[75]: Index([ 0,  1], dtype=object)

In [76]: data = """\
this, that, 0, 1
foo, 20, 30, 40
50, 60, 70, 80
"""

In [77]: df  = pd.read_csv(StringIO(data), index_col=[0, 1])

In [78]: df
Out[78]: 
             0   1
this  that        
foo  20     30  40
50   60     70  80

In [79]: df.index  # <-- 50 is string -->
Out[79]: 
MultiIndex
[('foo', 20L) ('50', 60L)]

In [80]: df.columns 
Out[80]: Index([ 0,  1], dtype=object)
```
