Marco is now a simple list dialect.
Rename a package.
Change grammar to allow non list forms on top level.
Add toString to Numbers and Strings.
Refactor eval and lookUp in tests.
Add test for symbol lookUp.
Add string representations test.
Add type checking for first argument of def.
Improve the test for type error on first argument of def.
def now returns nil.
Add arity check to def.
Readability changes.
Add test for using def as a value.
Check for already defined values when binding with def.
Fix bug that caused function parameters to fail to bind if closure env had a binding with the same name.
Add tests for function closures.
Add test for zero argument function.
Move exceptions into a package.
Add some checks to function argument lists.
Check for correct arity on function macro.