added optional support for node-source-map-support

I added optional support for ```node-source-map-support``` when running under node.js and not performing a build. This allows stack traces to display the proper CoffeeScript line/column during development.

I also changed the comments for source maps from ```//#``` to ```//@``` since they are natively recognized by node.js. Without this modification the eval'd source files in the stack traces show up as ```<anonymous>```.

This requires my fork of [node-source-map-support](https://github.com/ddude/node-source-map-support) in order to work. I've made a [pull request](https://github.com/evanw/node-source-map-support/pull/24) for this.