added test for external dependencies

[beatgammit]

Added a test that uses config.js to specify where external dependencies are. Directory structure:

• src
  • index.js - depends on extra
• deps
  • extra
  • extra.js
  • lib
    • helper.js
• config.js - {paths: { extra: "deps/extra/extra" } }

I relatively new to gulp, requirejs and CoffeeScript, so this test may need to be modified. The intent of the test is to emulate a relatively complex bower + requirejs setup.