Homework 10 due 4/27

All of this is based on the SplayTree.hs file discussed in class.  It can
be found on the main course webpage.

1.  Convert this to a module.

2.  Add a occurs function to the module.  It's signature can be seen in the
source code.  If the element is in the tree then it returns the pair
(True, newTree) where newTree has the same contents of the original tree
but has the element moved to the root.  And if it does not contain the element
it returns (False, oldTree) where oldTree is an exact copy of the original tree.

3.  Write a test main that tests all of the main functionality of the splay
tree.  It should do the following:

	1.  Import the splay tree module.
	2.  Create a random list of integers with 10 elements and insert
	    them into the tree.
	3.  Ensure that the flattened tree is identical to the sorted list.
	4.  Search for an element of the list and ensure that the flattened
	    list is unchanged and the elemented searched for is at the root.
	5.  Search for a different number that is not in the list and ensure
	    that searching for the element returns False.

4.  (Extra credit)  Write a delete function that removes an elemnt of the
tree.  The other elements should not have the depths changed significantly.