DataFrame.dtypes reports all object dtypes even if items aren't object dtype
I'm not sure if this is just an error on my part, but I have

``` python

>>> dataset
<class 'pandas.core.frame.DataFrame'>
Index: 17788 entries, 10000 to AFFX-r2-P1-cre-5
Data columns:
ID          17788  non-null values
Sample 1    17788  non-null values
Sample 2    17788  non-null values
Sample 3    17788  non-null values
dtypes: float64(3), object(1)

>>> dataset.dtypes
ID          object
Sample 1    object
Sample 2    object
Sample 3    object

```

As it can be seen, "dtypes" reports "object" for all, but the columns aren't really all of dtype object. Is this intended behavior?
