Added new example showing how background threads work.
Added AsyncTask example fragment.
Renamed ConcurrencyExample to ServiceExample. Added threadExample to distribution examples.
Merge branch 'master' into cm-concurrency-example

Conflicts:
	examples/concurrencyExample/src/main/java/io/realm/examples/concurrency/ConcurrencyExampleActivity.java
	examples/concurrencyExample/src/main/java/io/realm/examples/concurrency/RealmExampleActivity.java
	examples/serviceExample/src/main/java/io/realm/examples/service/RealmExampleActivity.java
Cleanup preparing for PR.
Merge branch 'master' into cm-concurrency-example
Cleanup autogenerated comments + added missing close to service example.
Deleted ServiceExample. Updated changelog.
Merge branch 'master' into cm-concurrency-example
Fixed PR comments.
Fixed bug when restarting ASyncTask.
Merge pull request #651 from realm/cm-concurrency-example

Added new threadExample. Removed old concurrencyExample.