refactor(tagsInput): change tagsInput global var to angular.module

Using a global variable that contains the app module of your angular
application isn't really best practice because it's unnecessary to
create a global variable. Just calling angular.module('modulename')
will get a handle to the already instantiated module.
fix(tagsInput): remove unnecessary spec that made the build fail

A previous commit introduced native ng event handlers. the Ng event
handlers always call a digest cycle when they are triggered. Therefore
this old spec was failing the build and doesn't reflect the code base
anymore.