Add grunt build

Maintaining the `Makefile` is going to get super annoying I think, using the grunt plugin can make this a whole lot easier it.

I moved the libraries we depend on into `src-lib/` so we can just include the `"src-lib/**/src/**/*.purs", "src-lib/**/src/**/*.purs.hs"` patterns for files in the build, and also this way we don't have to keep adding them to `.gitignore`.

Thoughts? I wasn't sure if we were sticking with the Makefile for some other reason. I guess doing it this way adds another dependency, but we're going to be dependent on the node ecosystem once purescript-in-purescript is done anyway.