Added support for iced-coffee-script with .iced and .coffee extensions

`iced-coffee-script` is an extension of coffee-script with some cool async features added. This PR fixes a few issues regarding `iced-coffee-script`:

- `node-config` does not parse files with the .iced extension. These are now parsed with iced-coffee-script.
- `node-config` breaks compilation for projects where `iced-coffee-script` is used with `.coffee` files. In this case, `node-config` parses a `.coffee` config file with `coffee-script` and registers it, so that all further `.coffee` files are compiled with `coffee-script` and not `iced-coffee-script`. `node-config` now parses `.coffee` files with `iced-coffee-scripts`, if it exists, and falls back to `coffee-script` if it doesn't.