Added demo to JSFiddle and additional feature

Per @peterfarrell,

>Added the ability to turn off/on the ability to have multiple emails separated by a , or ;. In my case, some of our email fields only allow one email address and allowing the enter key to append a 2nd or more address isn't good.

Just moved the changes to a non-master, pushable branch so I could clean up the README and add a manifest for versioning.