don't use relative path to spin.js dep

Problem:
If you're already using spin.js in your app, it would get loaded twice. Once from the path defined in your app's requirejs config and once from the relative path defined by Ladda.

Solution: Don't use relative paths in a library like Ladda.
add bower.json
compile latest js
Merge branch 'master' of github.com:hakimel/Ladda
compile latest js