Major clean up and documentation push.

Set is now fully-documented, with more extensive tests, bug fixes, and more
benchmarks. At this point Buffer and Set should be ready to go, we just need to
clean up Map as well.
Clean up specialization, comments, and benchmarks.

This commit mainly changes some signatures, does a bit of
re-formatting, and removes an unused benchmark.
Finish Map documentation, docs, tests, etc.

This commit gets all of Maps methods documented. It also introduces
some other changes:

1. Set and Map have a better ofSize() factory constructor
2. Renamed/Removed some map-esque methods on Map
3. Improved Map's test coverage
4. Fixed at least one correctness bug in Map

At this point, Buffer, Set, and Map have tests and docs.