Add fun1' and fun2'

fun2' was a killer for me. I barely stumbled my way to an answer.
Add naive foldTree with treeInsert

This is getting the wrong depth for the outermost tree, possibly others.
Refactor treeInsert; extract sprout to make leaves
Simplify treeInsert patterns

If both children Trees are not Leafs, we don't then need to deconstruct
a Node on each side, as the Leaf on either side will match.
Add xor

This is a logic-based version, as opposed to a [more appropriate?]
bitwise solution.
Add map'

This seemed a little too easy.
Add naive, incorrect version of myFoldl

After quite a bit of testing, my hopefulness was not rewarded :(
Merge branch 'hw4'