rubylisp extracted into a freestanding gem

gistfile1.txt

>: irb
2.0.0-p247 :001 > require 'rubylisp'
 => true 
2.0.0-p247 :002 > Lisp::Initializer.register_builtins
 => ... 
2.0.0-p247 :003 > Lisp::Parser.new.parse('(+ 1 2)').evaluate(Lisp::EnvironmentFrame.global).to_s
 => "3"