Added a post about dropdown issues in Angular.JS

Under forms, added the article:

Common Problems (And Solutions) When Using Select Elements With Angular.JS

http://gurustop.net/blog/2014/01/28/common-problems-and-solutions-when-using-select-elements-with-angular-js-ng-options-initial-selection/
Merge pull request #129 from Meligy/patch-1

Added a post about dropdown issues in Angular.JS