[FLINK-1070] Change return type of "getBroadcastVariable()" to List.

This closes #105
[FLINK-1075] Removed the AsynchronousPartialSorter.

This closes #104
[FLINK-1079] Fix inconsistent parameter naming
[FLINK-1078] PrintingOutputFormat uses same partition indexing as FileOutputFormat.
[FLINK-1084] Fix broken links in "How to add an operator"
Add Pi approximation Java example

This closes #78
Some simplifications to the PiEstimation example
[FLINK-1020] Introduce minBy and maxBy

This closes #101
[FLINK-610] Added KryoSerializer

This closes #74
Default generic serializer is Avro. Minor improvements in KryoSerializer. Add mini benchmark for Avro/Kryo.
Disable merging of Iteration Aux Tasks

This will become obsolete once we have buffer oriented execution.
Disable it for now because it is causing a bug: FLINK-1087
Fix DeltaIteration Bug with Immutable Types

The CompactingHashTable did not obey the new serialization contract that
allows for immutable objects. We must always use the return value of the
deserialization methods and cannot assume that the data was put into the
reuse object.
[FLINK-1086] Replace JCL with SLF4J and Log4j with LOGBack

- Excluded Kafka's transitive dependencies: jmxtools and jmxri
- Corrected encoder pattern in logback.xml
- Removed explicit logging access. Loggers are now configured by
  configuration files. Fixed Yarn issue with multiple logging
  bindings.

This closes #111.
[FLINK-1017] Add documentation for execution parallelism

This closes #114
Updated documentation figure: FlinkOnYarn.svg

This closes #110
[FLINK-629] getFieldNotNull added to Tuple and updated Aggregators and Comparators to use that where appropriate
[FLINK-629] Updated getFieldNotNull usage and added it to TupleSerializers

This closes #73
[FLINK-1063] Revert race introducing commit

This reverts "[FLINK-998] Close network connections when idle" [1] as
it introduced a race condition into the network stack, which might
result in a re-ordering of network envelopes.

[1] 52512636444902497e47ccbfb1cabaffb3e23343
[FLINK-925] Support KeySelector function returning Tuple types
[FLINK-925] Extended for distinct operator and added test cases

This closes #59