convert to ndarray, and check and adjust shape, with unit_tests
I tried to let pandas through, but it doesn't help. np.dot for example returns an ndarray.
I left the commented out code for testing DataFrame in the generic tests, but it needs special handling on before return.
I don't know if we have any wrapper code for predict. I didn't see any.
Some comments on the requirements
REF: Results.predict convert to array and adjust shape
@jseabold Do you know if there is any wrapper for predict, or any examples were predict returns a DataFrame with correct index?
This PR converts every exog to ndarray. subclasses need to handle extra arrays, like exposure in count models.
Coverage remained the same when pulling ada08b9 on josef-pkt:fix_predict_1032 into 01fd4a2 on statsmodels:master.
ready to merge IMO, unless there is a problem with DataFrames.