Removed ChangeLog (was only a 3-line helper file for myself)
Refactored car/cdr/cons
cons/car/cdr use general function interface now
NumArg error argument type changed to Int (from Integer)
Added mutable state (IORefs). Not yet added to evaluation procedure though.
Refactored if/quote evaluation, similar to what has been done to car/... in commit 2ac7977 before
Code alignment beautified
Mutable state implemented. (Basic functions existed since commit e8a2b1a, but were unused.)
Moved source to ./src folder