Add recursive implementation notes.
Change return type of copy to be specific.
Add AABB equals and hashCode methods.
Flip visitor args order for non-symmetric joins.
Add tests for contains queries.
Fix error in contained queries.
Add tests for contained queries.

Clean up contains query tests, pull Pair class into its own file.
Add extra test case to contained query.
Fix error in intersection queries.
Add tests for intersection queries.
Add extra test case to intersection query.
Remove manual test file.