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
Better naming, and new test

... using to compare 0.19 and 0.20 so want in both.
Fix the compiler warnings
Adding the hooks unsafeSubscribe by making the execution same as safe version without the safety checks.
Merge pull request #1397 from abersnaze/add-hooks-to-unsafeSubscribe

Adding the hooks unsafeSubscribe
Merge pull request #1396 from zsxwing/rxscala-fix-warning

RxScala: Fix the compiler warnings
Update Perf Tests

matching with work being done for 0.20 to allow comparisons
Merge pull request #1399 from benjchristensen/perf-tests-0702

Update Perf Tests
Internal Data Structures

Various data structures to allow performance improvements.
I am committing these separately from the code that uses it to keep the pull requests simpler.
Nothing in RxJava depends on these classes in this commit.
Merge pull request #1400 from benjchristensen/internal-data-structures

Internal Data Structures
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)