Post krealloc demo

Tree notes:
	You know how they work already
	Let's make one!

Considerations:
	It'll be a C++ ADT, like we've been doing
	This time I want a key/value tree
		key:  Used for ordering and finding nodes
		value:  Can be retrieved given the key
	Search given key must be O(log(n))
	Search given value can be O(n), like a linked list
	We'll do a template class
	It'll be a red/black tree
	We won't use the example from last term
		But we'll probably steal the tree visualization bit

Practicalities:
	Red/Black trees tend to have some bugs
	I'm going to add a couple active learning debugger exercises
		So log into isoptera.  We'll use /tmp for shared code

Limitation:  1 value per node
	Just to keep our heads screwed on straight

Required operations:
	key:  Can we standardize on two comparisons?
	value:  Just need to be able to get back a reference
	A set would just have keys
	Project 2 describes a tree with just values, not key/value pairs

Iterator-based traversal:
	Should all four ways be available?
	inorder:  It's good to print out values in order
	postorder:  We'll need one for the destructor anyway
	preorder:  Maybe less appealing
		It's good for duplication
		Also good for expression parsing, but we probably won't do that
	breadth-first:  log(n) memory, log(n^2) if fully unbalanced
		We won't be fully unbalanced anyway
		With limited depth, it'll give distributed samples
		Can be used to print tree structure
		Good lab idea!

Operators and Methods:
	add, remove, accessor for size
	begin and end for inorder traversal
	For a key/value tree, operator[] is sort of expected
		Can it be used to add a new value?  Some libraries do this.
	I'd like operator<<, mostly just for debugging
	write_graph or something to do graph output
	
Parent pointers:
	Could we do without?
	Let's see what trouble we run into!