Added Callbacks And Tag Pool

If you accept this pull request you will be able to create tags restricted to pre-defined tags from a pool of tags (optional and case-sensetive). Also you will have the option for callbacks which pass the tag by argument, please check out http://lewiscowles1986.github.io/TagTagger.js/demo/taggerDemo.html?1 for a demo (for some reason GitHub requires a get variable to overcome caching at least within my home...)

ENJOY + Thanks for the CoderBits Post mentioning this awesome project