split out repl

can the repl code be split out so that it's it own callable module?

that way I can use something like:

``` livescript
ls = require 'LiveScript'
# ... bunch of code
ls.repl.start!
```

Would be really useful when experimenting with code or debugging, interactive break points.  Bonus: hitting ctrl-D breaks out of the repl and resumes normal control flow.
