added 'forever' and fixed handling of break/continue in other loop constructs
fixed handling of break/continue loop constructs, again
added local scope to all loop constructs
removed 'repeat' from keyword list; it's now do...until
updated grammar.md
added !=
added rosetta__Hello_world__Web_server
updated grammar.md
started adding bitwise operations
beginning effort to add threading and futures
fixed list comprehension parsing (broken by adding divides predicate)
continuing effort to add threading and futures
added Environment class towards threading and futures support
added Environment class
moved datatypes info Module class
synchronized shared data (symbol maps)
started implementing runnable() method of Closure
moved call() outside Evaluator.apply() making it a method of Evaluator
moved Activation, Closure and Environment into Evaluator as inner classes
added runnable() method to Closure to get a wrapped Closure that runs in its own execution environment