hello world language
add float and bool
add nil type
add dummy symbol, need to add eval
resolve symbols, had to include Cc, Env and Error hierarchy

moved almost all code to subclasses to make it compile on pypy
pair eval and operatives
add applicative, and expand to pair
add parser, run from stdin
fix Str.to_str
add do operative
add def operative: echo '(do (def name "bob") (display name))' | ./plang-c
memoize size of pairs
hierarchical Env, Lambda type and lambda operative
make lambda and do work correclty
add a simple working example
implemente call/cc