Add quote and atom.
Convert '... to (quote ...) in str_to_array.
Add support for more functions. There are some bugs/undefined behaviour around when to wrap values in Literals. Worth investigating if we need literals at all.
Remove Literal in favour of using the values directly. Add Symbol class to handle symbols.
Fix load function
Convert static symbols to strings after evaluation.
Add cond and lambda. Lambda doesn't yet support other lambdas as arguments.
Add comment for lambda
Merge branch 'master' into scheme-compliance

Conflicts:
	pisp.py
Merge pull request #6 from hazz/scheme-compliance

Scheme compliance