Now backed by MemDOWN instead of StringMap

Still need to write tests for persisting data across instantiations,
and load data from the LevelUP store on instantiation
Changing things around to be less stupid
whoops
Lots of little changes, still need to rewrite tests

Getting local/all posts is pretty broken up into different functions
now.

Used the asynquence library to make the PostManager suck less.

The main functions take options objects instead of various arguments
that were getting confusing.
All tests passing with the new getPosts({options}, cb) setup
Reorganized classes, levelUP persistence tests

- Moved the index managing and post managing classes out to their own
file modules in lib/
- Renamed some files that had camelCase instead of underscores
- Wrote another persistence test for levelUP
Merge branch 'levelup'