Neater build

Added missing LiveScript dev dependency.

Put compiled files under `./lib` where they can easily be git-ignored.

Told `npm` to keep only the compiled sources (`./lib` and `run.js` and
`readme.md`) when publishing.

Made `run` the entry-point, so LS compilation can be a dead simple `lsc
--output ./lib --compile`. Made the entry point only generate on `npm
install` to reduce potential confusion trying to run when not compiled
yet.