Topics upgrade

- Adding NPM, Browserify, and AngularJS
- Changes in topic 1 to use Spotify API
- Removed topic on Template Engines. Replaced by a topic on AngularJS (which is basically a Template Engine on steroids).
- Removed RequireJS from the modules topic. Added a basics of NPM, and Browserify. Understanding CommonJS is helpful if the student wants to become a NodeJS developer. 

Future Pull Requests may include an addition on ES6 Modules (as they are used by ember-cli, for instance).
Change url to http://javascriptweblog.wordpress.com/2011/05/31/a-fresh-look-at-javascript-mixins/