Cross-reference observeOn and subscribeOn from each others' javadocs
CompositeException does not mutate nested exceptions by attaching stacks, but instead
aggregates them at print-time.

Since nothing is being mutated, there's no chance of accidentally creating a cycle in the Exception chain.
Removed unused import
Fixed up SafeObserverTest w.r.t. CompositeException changes
Merge pull request #1388 from mattrjacobs/eliminate-circular-exception-creation

CompositeException stops mutating nested Exceptions
rxjava-scalaz

commenting out rxjava-scalaz until I can figure out what's wrong with the Netflix building system that prevents it from finding the following jar:

```
Artifact 'org.scalaz:scalaz-core_2.10:7.0.4@jar' not found.
```
[Gradle Release Plugin] - pre tag commit:  '0.19.2'.
[Gradle Release Plugin] - new version commit:  '0.19.3-SNAPSHOT'.
Version 0.19.2