Refactored lib and test to make everything more maintainable

**Minor release**

I began working on fixing #17 but got frustrated at the growth that `eight-track` has turned into. In order to get a hold on things, I have performed the following:

- Removed `lib/store` and created https://github.com/twolfson/fs-memory-store
- Consolidated `Connections` into `Message` class (they all feel the same)
- Relocate premature class method abstractions onto prototypes (e.g. `Message.getResponseInfo`)
- Broke down 500+ line test file into many separate files
- Swapped out `test/utils/http` for `request-mocha`

/cc @mlmorg @zheller @Raynos