Add SQL arithmetic operators as binaryMethods
Let binary expressions (e.g. boolean AND, OR, =, or arithmetic +, -, ...) be composable
Fix nits; capitalization and spaces.
Fix up errors caught by jshint
binary clause dialect test
Break out ValueExpressionMixin into its own file, and mix it into the value expressions BinaryNode, UnaryNode, and Column.  Will make composing such value expression nodes easier in the future.
whoops, accidentally pushed when not ready.  fixed some bugs in previous commit
Mixin only once.  Set flag to true once mixed
Add tests implementing simple formulas to test composing binary expressions.
Cleanup for jshint