Added support for SXXEXX filename formats:

 - added a regex to handle filenames that include both a number in the
   name of the show (e.g. Warehouse 13) and have SXXEXX in the filename
   (e.g. S05E07).
 - added unit test for this specific filename (Warehouse 13) and a bunch
   more recent example filenames to the test.
Made the ShowStore concurrency less lock-y:

 - removed the semaphore and changed the underlying show store Map to be
   a SynchronizedMap which will handle the concurrency instead
 - performance seems to be much better for multiple show renames, since
   the threads aren't waiting for a lock anymore