removes the -count method from the persistent map protocol because it is has been moved to Counted
Use java's AtomicReference to back atoms. Add compare-and-set-entity! into the platform.
Add test to show atomicity of swap!
Merge pull request #2 from patrickgombert/atomic-reference

Use java's AtomicReference to back atoms. Add compare-and-set-entity! in to the platform.
refactors platform methods
cleans up map entry equals
clean number ops
Implement get/3, allowing for user specified not-found
Merge pull request #3 from patrickgombert/default-get

Implement get/3, allowing for user specified not-found
refactors equality and comparable into comparison; adds addition for int types