[Gradle Release Plugin] - pre tag commit:  '0.18.3'.
[Gradle Release Plugin] - new version commit:  '0.18.4-SNAPSHOT'.
Update according to review in issue #1159
Remove 'startWith', add '+:' and ':+'
Update 'startWith' info in CompletenessTest
Change to batch dequeue.
Fixed synchronous ConnectableObservable.connect problem
GroubByUntil to use BufferUntilSubscriber
Add facilities for creating Observables from JavaFX events and ObservableValues.

Provides:
 * a Scheduler implementation ensuring execution in the JavaFX UI thread
 * a Subscription implementation ensuring that un-subscription happens in JavaFX UI thread
 * an Observable factory method for observing UI events on JavaFX nodes
 * an Observable factory method for observing value changes of a JavaFX ObservableValue

Also the rxjava-javafx is added to the gradle build.
Switch to direct accept and no instanceof
Version 0.18.3
Make sure to shut down executor when NewThreadScheduler is unsubscribed
Add note to javadocs about ConnectableObservables requiring connect() call (#1180)
Fix issue #1187
Update the signature of "schedule" methods
Fix attempt #1
Negative schedule time now indicates immediate execution.
Fix issue #1196 and some docs issues
Comment explaining non-positive delay values
Adding marble diagrams to StringObservable operator javadocs