Add support for ngModel refresh

Refresh the chosen element after the underlying model changes.
adding comments
Update chosen.coffee
Update chosen.js
Update chosen.coffee

Made ngModel optional and added width to allowed attributes.
Update chosen.js

Added width, made ngModel optional and removed whitespace
Update chosen.coffee

remove extra commas
Update chosen.coffee

Adding conditional for case of no ngModel
Update chosen.js

Updating with changes for case no ngModel
Merge pull request #12 from LukeMason/master

Adding support for ng-model changes