applymap and misc/float columns
This works as expected in latest pandas:

```
> df = pandas.DataFrame(data=[1,"a"])
> print(df)
   0
0  1
1  a
> print(df.applymap(lambda x: x))
   0
0  1
1  a
```

This does not (note the float "1." instead if "1"):

```
> df = pandas.DataFrame(data=[1.,"a"])
> print(df)
   0
0  1
1  a
> print(df.applymap(lambda x: x))
     0
0   1
1 NaN
```

This is a problem in statsmodels/statsmodels#636

pandas.**version** -> '0.11.0.dev-14a04dd'
