[FLINK-1222] Tasks send close acknowledgements early.
[runtime] In local mode, make sure taskmanagers have completed registration before starting a job.
[FLINK-1215] Fix spurious failures when creating output directories due to I/O races
[streaming] Updated streaming groupBy operators to allow grouping on field expressions
[streaming] Aggregation rework to support field expression based aggregations for Pojo data streams
[streaming] Pojo wordcount example added to streaming
[FLINK-1224] [streaming] getExecutionEnvironment method fixed to work properly for StreamExecutionEnvironment