Rewrote keys with explicit recursion
Rewrite t_foldl'. It was not testing anything.
Rewrite t_unionR using ===
Rewrite t_deleteMin using ===
Rewrite t_deleteMax using ===
Rewrite t_insert_present and t_insert_missing with ===
Merge pull request #48 from kgeorgiy/keys

Rewrote keys with explicit recursion
Merge pull request #50 from mikesteele81/update-tests

Update tests
Remove trailing whitespace :-(
Remove redundant type witnesses
Simplify t_insertWith_present and t_insertWith_missing