[FLINK-953] Remove fake tail from iterations

This closes #124
[FLINK-1077] Improved error message if test fails

This closes #120
[FLINK-1096] Correction to histogram accumulator

This closes #117
* each key is associated with the number of times it was inserted into the accumulator
* backed histogram with a tree map to present the entries sorted by key
[FLINK-1038] added RemoteCollectorOutputFormat

This closes #94