Add type parameters in OutboundConnectionQueueTest

The use of PowerMock's Whitebox without type parameters led to compile
problems with Java 6.
Remove unused import from OutboundEnvelopeEncoderTest
[FLINK-1039] Fix pojo expression keys for group reduce
[Docs] Limit nesting of generated TOCs

The jekyll tocify plugin generates an HTML TOC based on the headings
of the markdown files. This commit limits the nesting of the TOC to 2,
which means that only h1 and h2 element will be taken into account.
Previously, all heading elements were used, which resulted in a very
cluttered TOC.
[Docs] Adjust Java API documentation to be in sync with latest changes

[ci skip]
[FLINK-701] Refactor Java API to use SAM interfaces. Introduce RichFunction stubs for all UDFs.
[FLINK-701] Several cleanups after SAM refactoring.
  - Lambda detection compiles on earlier java versions
  - Add lambda detection test.
  - Fix JavaDocs
[FLINK-701] Change KeySelector to a SAM interface

This closes #85
[FLINK-1023] Switch group-at-a-time function to java.lang.Iterable (from java.util.Iterator)
Iterables over transient data throw an TraversableOnceException when iterated over again.

This closes #84
Create release scripts, add support for "cdh4" build.