CompositeException

- reverting to version that just does printStackTrace
- see https://github.com/ReactiveX/RxJava/issues/1405
printStackTrace and getCause implementation

The printStackTrace and getCause implementations have different approaches to handling circular references.
If on a JVM where printStackTrace is called directly, the full causal chain will always be printed. If on one such as Dalvik
where getCause is invoked directly then it will cut the causal chain if it sees a duplicate.
Merge pull request #1632 from benjchristensen/composite-exception

Composite Exception - Circular Reference Handling
[Gradle Release Plugin] - pre tag commit:  '0.20.1'.
[Gradle Release Plugin] - new version commit:  '0.20.2-SNAPSHOT'.
0.20.1
Javadoc enhancements for new CompositeException implementation (mostly formatting).