Add convenience method for adding unsubscription callback
rename variable childObserver to child (is now a Subscriber) and rename gps to group (is not plural)
Merge pull request #1301 from jbripley/subscription-block-expression

RxScala: Add convenience method for adding unsubscription callback
Add flatMap variants to RxScala
Add concatMap to RxScala
Merge pull request #1304 from zsxwing/flatMap

Add flatMap and concatMap to RxScala
Merge pull request #1302 from davidmoten/groupBy-naming

improve variable names in OperatorGroupBy
0.19.0-SNAPSHOT
everything defaults to 1.6
Hooked RxJavaPlugins errorHandler up within all operators that swallow onErrors.
* Otherwise, the only onErrors visible to plugin are the ones which propagate all the way to SafeSubscriber.
testNotificationDelay - Attempt at determinism
Merge pull request #1307 from benjchristensen/make-notificationDelay-deterministic

testNotificationDelay - Attempt at determinism
Remove call to RxJavaPlugins ErrorHander in mergeDelayError operator - CompositeException is already visible
Merge pull request #1306 from mattrjacobs/add-error-handler-to-error-swallowing-operators

Hooked RxJavaPlugins errorHandler up within all operators that swallow onErrors
Hide ChainedSubscription
Merge pull request #1309 from benjchristensen/subscriber-subscription

Hide ChainedSubscription/SubscriptionList from Public API
[Gradle Release Plugin] - pre tag commit:  '0.19.0'.
[Gradle Release Plugin] - new version commit:  '0.19.1-SNAPSHOT'.
0.19.0