pd.DataFrame converts np.uint64 greater than 2**63-1 to objects
My question is based on this post I found:
http://stackoverflow.com/questions/34283319/pandas-converts-large-unsigned-integers-to-object-types

The maximum value for np.uint64 is (2^64)-1 so why does pandas convert np.uint64 types greater than 2^63-1 to objects when converting arrays to dataframes. pd.to_numeric() also fails to convert these values back to np.uint64.
