Adding support for spin.js 2.0.1

I'm building an Angular Application, I've been using Ladda a long time ago and this time I'm using the spin.js in a directive (https://github.com/urish/angular-spinner) but this module uses Spin.js#2.0.1 and when I check my Ladda buttons they didn't work properly so I noticed that Ladda uses 1.3.x and that was the bug. So I decided to upgrade spin.js in Ladda :)

Regards,

Kevin