BUG: Fix dtypes order when ordering is different from original file in pandas.io.stata.read_stata
This fixes http://stackoverflow.com/questions/31783392/pandas-adding-columns-to-filter-will-mess-with-data-structure
The dtypes of the DataFrame returned by read_stata have the same order as the original stata file, even if columns are specified with a different order.

@jreback much cleaner now
 lgtm. minor doc comment. ping when green.
 @jreback good to go
 thank you sir!
