EAGLESIX-2708 expression Subtract ported to mongo 2.6.5
Merge branch 'feature/mongo_2.6.5_expressions' into feature/mongo_2.6.5_expressions_Subtract
EAGLESIX-2708 Fixed test cases
EAGLESIX-2708 Removed unused lines
EAGLESIX-2651: Date: fix minor bugs during review
Merge pull request #25 from RiveraGroup/feature/mongo_2.6.5_expressions_Subtract

expression Subtract ported to mongo 2.6.5