fix(tagsInput): Added support for Angular 1.2.x

- Implemented transclude-append directive in order to re-create the old
  behavior of ng-transclude so the autocomplete feature works and the
  tagsInput directive's template remains well-structured.
- Replaced element.bind() with element.on() since starting with v1.2
  bind() is just an alias for on();
- Fixed isolate scope retrieval in all tests;

Closes #17.
chore(doc): Adjusted documentation tags

Adjusted documentation tags for optional parameters so they comply with
JsDoc/NgDoc format.
refactor(tagsInput): Changed options initialization

Refactored options initialization code in order to make it simpler and
easier to be extracted into a service in the future so the autocomplete
directive can make use of it.

BREAKING CHANGE: The ngClass option was renamed as customClass so it's
clear that that property is just a value and not the ngClass directive.
chore(grunt): Refactored Gruntfile

Refactored Gruntfile into using load-grunt-tasks package so the script
doesn't have lots of loadNpmTasks calls
chore(build): Updated build files