Re-added rails build support.

Was sad to see support for rails pipeline go, any particular reason other than the clunkiness of my previous example.

Anyway, I've made it a bit better, to build the rails version do either `grunt build --rails` or `grunt dist --rails`.

**If you run `grunt --rails` (without a task) it probably won't work too well, as the examples/template don't reflect the rails-friendly paths.**