Replaced single scope with a stack.
Moved to a better scope object.
Add -> for upcoming functions.
Add tests for mapsto.
Rearrange what is considered an expression.
Tests now passing.
Moving towards functions that actually work.
Function calls working, next up passing variables.
Closer to having functions still.
Unary functions now kind of work.
Merge pull request #14 from mightymoose/master

Unary functions, sort of.