Implementation of Realm.cancelTransaction
Update SharedGroup.java
Updating documentation and using IllegalStateException.
Update Realm.java
Update Realm.java
Merge branch 'master' of github.com:realm/realm-java into kg-rollback

Conflicts:
	changelog.txt
Merge branch 'kg-rollback' of github.com:realm/realm-java into kg-rollback
Merge pull request #499 from realm/kg-rollback

Implementation of Realm.cancelTransaction