Adds a benchmark test

This adds a file to the Test target that benchmarks each operation.
Improve performance of Array operations

This diff just includes a few small performance tweaks.
Improve performance of Dictionary operations

A few more small performance tweaks...
Improve performance of Set operations

Similar small perf tweaks as for Array...
I'm apparently an idiot who can't resolve a merge conflict correctly...
... *sigh*
Silly...those go in the other pull request!
...cache invalidation, off-by-one-errors, and...somethingsomething
ARC is magic!
Now with OrderedSet speed enhancements as well!
Merge pull request #5 from jballanc/speed-improvements

Conflicts:
	ConcurrentCollectionOperations/NSArray+ConcurrentCollectionOperations.m
	ConcurrentCollectionOperations/NSDictionary+ConcurrentCollectionOperations.m
	ConcurrentCollectionOperations/NSSet+ConcurrentCollectionOperations.m