refactored web REPL and added colour
display negative numbers with '~' instead of '-'
share context between commands in REPL
lexer: prepend ^ to regexes only once

This speeds up the parsing process by another 50%, roughly.
simplified function wrapper around compiled code

sing "eval()" and explicit parameter names instead of "new Function()" and the "arguments" object.
Merge branch 'master' into gh-pages
built web UI