w04: Adding BST.hs
w04: Moving BST tests into Week4Spec
w04: Adding stubs and BST
w04e01: ex1
w04e02: ex2
w04e03: ex3
w04e04: ex4
w04e05: ex5
w04e06: ex6
w04e07: ex7
w04e08: ex8
w04e09: ex9
w04e10: ex10
w04e11: ex11
w04e12: ex12
w04e13: insertBST
w04e14: allCaps
w04e15: dropTrailingWhitespace
w04e16: firstLetters
w04e17: asList