Merge branch 'feature/mongo_2.6.5_expressions_Let' of https://github.com/RiveraGroup/mungedb-aggregate into feature/mongo_2.6.5_expressions_Let
EAGLESIX-2695 Added a new test file. Populated it with some tests and some test stubs.
EAGLESIX-2695 Fixed some broken test cases.
Merge branch 'feature/mongo_2.6.5_expressions' into feature/mongo_2.6.5_expressions_Let
EAGLESIX-2695 bugfix. restored the check that ensures two arguments are passed in. Added rudimentary test cases.
EAGLESIX-2695 Added the check for the number of arguments. Added rudimentary tests.
Merge branch 'feature/mongo_2.6.5_expressions' into feature/mongo_2.6.5_expressions_Let
Merge branch 'bugfix/mongo_2.6.5_expressions_Let' into feature/mongo_2.6.5_expressions_Let

Conflicts:
	test/lib/pipeline/expressions/LetExpression_test.js
Merge branch 'feature/mongo_2.6.5_expressions' into feature/mongo_2.6.5_expressions_Let
EAGLESIX-2695 Improving the tests, correct code bugs. More To Come
EAGLESIX-2695 More improvements, with More To Come.
EAGLESIX-2695 Corrected a bug in ObjectExpression that would cause optimizations to be dropped on the floor. Continuing to work through $let test cases.  More To Come.
EAGLESIX-2695 Completed all test cases expect a full blown test that requires expressions that are not yet available.
EAGLESIX-2695 Fiddled with the test cases.
EAGLESIX-1695 in preparation for another merge with expressions
Merge branch 'feature/mongo_2.6.5_expressions' into feature/mongo_2.6.5_expressions_Let
EAGLESIX-2695 The Gauntlet, a reasonably thorough test case, works.
EAGLESIX-2695 fixed a typo, put a call-out in the test for Kyle's descerning eye.
EAGLESIX-2695 it is easier to fix the typos now...
EAGLESIX-2651: Nary: fix failing tests, related bugs