Better node/REPL CLI

[rcarmo]

As things stand, the wisp binary acts as a compiler if things are piped in and invokes a REPL if there are no arguments.

Since I'm starting to use wisp with node for some CLI stuff, I propose the following changes so that we can skip intermediate JS files or at least tidy things up a bit:

• -h for usage
• -r to get a REPL
• -c to compile all subsequent arguments
• set the output file via -o (or default to compiling to separate files)
• if the above are missing, compile and run the first argument, starting with a -main function (that gets argc and argv, etc.)

It would also be nice to have a better idea of how to load the runtime libraries at the REPL (I'll gladly add that to the README if you'll give me some hints!).

[Gozala]

@rcarmo I agree --help is needed, I just have not got to write it. As of other options I would rather see external wrapper tool instead of adding all of this extra args to wisp binary itself.

[robjens]

May I also recommend https://github.com/danielgtaylor/nesh? I found it very pleasant to work with in CoffeeScript and it seems to be extensible although I have no idea how hard/easy it would be to make it fit.