Version 2

- Refactor Public API
  - Public API is now just Segment and model classes for server and
    to look up stats
  - Replace JSONObject with Map compatible implementation.
  - Allow users to construct their own instances of the client, but also
    manage a singleton for them if needed.
  - Context renamed to AnalyticsContext to avoid confusioin with
    android.content.Context
- Switch to Tape over SQL
- Surface user errors early
- Use handlers over just plain threads