Removing SyncService interface

- Removes interface
- Removes BasicSyncService implementation

refs #51
Replace uses of SyncService with Executor

Refs #51
Replace use of BasicSyncService

Refs #51
Update mock uses of SyncService

refs #51
Use MockExecutor in unit tests

Refs #51
Merge branch 'develop' into feature/executor
Merge branch 'develop' into feature/executor

Conflicts:
	Simperium/src/instrumentTest/java/com/simperium/BucketTest.java
	Simperium/src/instrumentTest/java/com/simperium/PersistentStoreTest.java
	Simperium/src/main/java/com/simperium/android/AndroidClient.java
	Simperium/src/main/java/com/simperium/client/Channel.java
	Simperium/src/support/java/com/simperium/test/MockBucket.java
	Simperium/src/support/java/com/simperium/test/MockClient.java
	Simperium/src/support/java/com/simperium/test/MockExecutor.java