EAGLESIX-2651: initial port of MinMaxAccumulator from v2.6.5
Merge branch 'feature/mongo_2.6.5_accumulators' into feature/mongo_2.6.5_accumulators_MinMax

Conflicts:
	lib/pipeline/accumulators/MinMaxAccumulator.js
Merge branch 'feature/mongo_2.6.5_accumulators' into feature/mongo_2.6.5_accumulators_MinMax
EAGLESIX-2651: MinMax: combine Min and Max tests into MinMax file
EAGLESIX-2651: MinMax: update tests for 2.6.5
EAGLESIX-2651: MinMax: tabs beats spaces
Merge pull request #18 from RiveraGroup/feature/mongo_2.6.5_accumulators_MinMax

Feature/mongo 2.6.5 accumulators MinMax