Merge Java Repo into Android Repo

[tyvsmith]

Proposal to merge http://github.com/uber/rides-java-sdk and https://github.com/uber/rides-android-sdk into one repo with multiple modules/artifacts.

Problem: To reduce overhead of decoupled releases, most use-cases cutting across both repos, and better discoverability.

Concerns: Folks building the java modules without having the android toolchain.

Thoughts?