analyze_tandem_dupes2.py: column names set at beginning of code rather
than in main.

generate_null_distribution.py: colnames put at beginning of code rather
than in main.

jplots.py: plot_tandem_tss function saves instead of shows the plot. 

set_directories.py: added a class for handling directories.

tandem_data.py: added code to indicate obsolete-ish code (to be
deleted!?) and also prints row on ValueError.

visualize_tandem_pairs.py: automated to produce plots for ALL 23
chromosomes. 

find_exon_locations.py initial commit: parses exon starts correctly.

ref_and_tandem.py: to be used as class for reading two files at a time.