Initial RxLost work

[sarahsnow1]

Overview

Begins rxlost module work with creation of new rxlost and rxlost-sample modules . Adds rx wrapper APIs around LostApiClient#connectionCallbacks

Proposed Changes

• Following Rx conventions, creates new ConnectionStatus enum to replace calls to ConnectionCallbacks
• Creates Observable<ConnectionStatus> to handle notifying subscribers when the client has been connected
• Creates new RxLostApiClient object which wraps LostApiClient and exposes getConnectionStatus() Observable
• Adds test coverage for new functionality
• Updates Rx sample app to demonstrate new functionality
• Updates gradle build tools version and target/compile sdk version

[ecgreb]

👍