[saksham219]

parse_gctx() function uses h5py to parse gctx files. h5py only takes indexes in a sorted order. To subset gctx files in the order indicated by the user, I have made some modifications to parse_gctx and associated functions to sort the dataframes returned by h5py according to the order indicated in the function call.

Other changes

• added new test cases to test_parse_gctx (both python2 and python3) to test for cases where sorting is set to False.
• absolute paths for example gct files in test cases and addition of init.py to test case directories so that all test cases can be run from one place in editors.
• function documentation changes.
• less complicated travis config