Update GoogleAnalytics.
Nfc: Fix auth error.
Update OkHttp.
Core service: Notify SyncManager on connectivity changes.
SyncManager: Partial rewrite for better error handling.

- Requests are posted in an event driven fashion with single
short-lived one-shot Runnables, rather than using a long-running
polling background thread.

- Requests are only written to disk when they cannot be posted
immediately.

- Thermo requests are never written to disk; the data is not
considered important enough to save when offline.
May revisit this if there enough interest.

- ConnectivityManager is consulted for connectivity before
performing some operations.  This will cut down on spurious
errors in the logs.
Ignore some javadoc warnings.
Crashlytics integration.
Eclipse: disable refactoring history.
Pour activity: dismiss progress dialog on new flow start.
Home activity: show an alert when the network is down.

Closes #47.