Created test cases that show inconsistent error handling with OnNextValue and toString
Fixed OnNextValue to not call toString on the failing value
Added a renderValue function to create a string from unknown client objects without calling toString (PR #1401)
Add links to Graham Lea's useful overview of observeOn/subscribeOn
Kotlin M8
Merge pull request #1406 from MarioAriasC/master

Kotlin M8
Avoiding OperatorObserveOn from calling subscriber.onNext(..) after unsubscribe().

The OperatorObserveOn operator uses a scheduler to cancel subscriptions as well
as to deliver the objects passing through it's onNext(..) in the right context.

Calling unsubscribe will schedule the actual unsubscription while not making sure
that the child subscriber will no longer receive calls to onNext(..) after
unsubscribe() returns.

This fix makes sure that after unsubscribe() returns no more onNext(..) calls will be
made on the child subscribers.

Signed-off-by: David Marques <dpsmarques@gmail.com>
Merge pull request #1409 from dpsm/master

Avoiding OperatorObserveOn from calling subscriber.onNext(..) after unsu...
Merge pull request #1401 from samhendley/onnextvalue

OnError while emitting onNext value: object.toString
0.19.4-SNAPSHOT

Manually incrementing as the upload to Maven Central for 0.19.3 failed part way through and can't be redone.
[Gradle Release Plugin] - pre tag commit:  '0.19.4'.
[Gradle Release Plugin] - new version commit:  '0.19.5-SNAPSHOT'.
Version 0.19.4
Backpressure & 0.20.0-RC1
Merge pull request #1412 from benjchristensen/backpressure-9

Backpressure & 0.20.0-RC1