Cleaned up top-level readme a bit (removed outdated things)
Cleaned up top-level readme a bit (removed outdated things)

* Remove produce/actor from common features list
  (actor is not common yet anyway)
* Added CoroutineExceptionHandler to the same section as SupervisorJob
* Removed Rx 1.x from integrations list
* Added Play Services Task and SJF4J to the short description of
  integration modules

Kotlin/kotlinx.coroutines,Kotlin/kotlinx.coroutines,Kotlin/kotlinx.coroutines,Kotlin/kotlinx.coroutines,Kotlin/kotlinx.coroutines