[FLINK-1073] Added test case to reproduce error
[FLINK-1073] Enables sorted group input for GroupReduce combiners.
- GroupReduceCombineDriver uses separate comparators for sorting and grouping.
- Adding support for multiple comparators for a single input driver required some refactoring.

This closes #109
[FLINK-1104] [streaming] Eliminated Tuple1 from connectors
[streaming] Streaming jobgraph and vertex refactor to match recent runtime changes
[streaming] added batchReduceGroup, windowReduceGroup functionality to ConnectedDataStream and GroupedConnectedDataStream
[FLINK-1102] [streaming] Projection operator added to DataStream

Conflicts:
	flink-addons/flink-streaming/flink-streaming-core/src/main/java/org/apache/flink/streaming/api/datastream/DataStream.java

Conflicts:
	flink-addons/flink-streaming/flink-streaming-core/src/main/java/org/apache/flink/streaming/api/JobGraphBuilder.java
	flink-addons/flink-streaming/flink-streaming-core/src/main/java/org/apache/flink/streaming/api/StreamConfig.java
	flink-addons/flink-streaming/flink-streaming-core/src/main/java/org/apache/flink/streaming/api/datastream/ConnectedDataStream.java
	flink-addons/flink-streaming/flink-streaming-core/src/main/java/org/apache/flink/streaming/api/datastream/DataStream.java
[streaming] Fixed InternalStateTest to avoid printouts + minor StreamVertexTest fix
[doc] [streaming] Added Twitter connector & Projection operator to docs