CoffeeScript REPL based on Node REPL

Per discussion in #2626, here's a pull request to replace coffee's hand-rolled REPL with a REPL that heavily leverages Node's REPL implementation by implementing a custom line eval function.

http://nodejs.org/api/repl.html

With this you get all the features of the Node REPL including tab completion, commands and the ability to provide any of the options to the coffee REPL that you can pass to Node's.

What you don't get is multi-line mode. It looks possible but will require some serious overriding of the Node REPL's line input handling.