group_miso_results.py:
get_intersection_of_files(): removed print per sample and added print at
end of function to signal how many common files exist across samples.
renamed function combine_miso_outputs_across_samples() to
consolidate_miso_across_samples(). It now calls two functions, one to
write header the other to write the body.
Added a make directory function to create directory if it does not
exist.

Write header function is now called write_combined_miso_header()

Created psi and logscore writer called write_combined_psi_logscore()