Makefile + .gitignore
This is a needless conversion, simplifying
Added parsing numbers

Also now there's only NumLiteral, which is underlyingly a f64. I think
this is how scheme actually works?
This string->slice conversion was also needless
Implementing quoted atoms

Right now this doesn't compile because of a borrowing error. I want to
fully understand why this error happens with this code and what I can do
about these sorts of errors in general.