Added functions to clean data and sort by year
Added collision detection
Made function to return intervals
Finished algo to find longest interval in interval set
Fixed bug where there are only two items in list, nothing returns
added pdb tracing for debug
Updated sorting function to sort by year and month
Updated test
Changed the way months are calculated.  found bug in combine script
Corrected error in the way months were calculated
Found another error in calculating months
Fixed an error in combine dates