Adds bootstrap3 styling as proposed at https://github.com/sciactive/pnotify/issues/60
Adds small documentation on how to use bootstrap3

Idea taken from https://github.com/sciactive/pnotify/issues/60#issuecomment-23206901
Changes "alert-info" to "alert-warning" as suggested by @Diaoul
Adds minified version
Merge pull requests #64 and #81.

Merge @koppor bootstrap3 #64 koppor/bootstrap3.
Merge @jugautam fontawesome #81 jugautam/master.
This should also resolve PRs #78 #76 and makes reference to open issues #82 #72 #62 #60 and if all parties can agree.