Removed hand-written bootstrap skeleton.

I'll be taking a different approach to bootstrapping, either by using Racc or by
hand-generating the AST. This should be much easier than writing the entire
initial parser by hand.
Refactored ruby-ll's own grammar.

It does not yet include any rules but it's much more compact due to the usage of
the various available operators (which I can now use due to not having to write
a parser manually).