use a set to parse the categories instead of heard coding them for the menu

# Lab 10
Task: Make a movie category app

Version History
1.0--10/22/2018--Initial commit, logic written.
	--Menu option to display list of movie titles, categories, or movies by category. 
	--Movie class written, accepts multiple categories per movie
	Known Issues
	--No method to add Movie Objects to the Movie List
	----(must add method to handle dynamic Movie class titles.)
	--editing
	--UI cleanup
	--comments
	--add ordering (alphabetical)
	--does not update list of categories.