created song and audiofile models
Changed audiofile model to a less specific more reusable model
working on the songs controller, changed again the audiofile model, to include the url field
added button and JS to add audiofiles as nested form properties, labels not working yet
changed style in add sogns form
added javascript to kill forms for audiofiles except if there is just one
Merge pull request #2 from xsimov/add-songs

Add songs