Added week 4 assignment project
Implemented methods weight and chars for week4/part1
Implemented method times for week4/part2
Implemented method makeOrderedLeafList for week4/part2
Implemented method singleton for week4/part2
Implemented method combine for week4/part2
Implemented methods until and createCodeTree for week4/part2
Implemented method decode for week4/part3
Implemented method encode for week4/part4a