Update README.md

Cleaned up the Courses section. Removed a couple of courses, and added the following:
* [Pluralsight: AngularJS Patterns: Clean Code] (http://www.pluralsight.com/courses/angularjs-patterns-clean-code)
* [Pluralsight: AngularJS Line of Business Applications] (http://www.pluralsight.com/courses/angularjs-line-of-business-applications)
* [Building Mobile Apps With the Ionic Framework and AngularJS] (http://www.pluralsight.com/courses/building-mobile-apps-ionic-framework-angularjs)