Update index.md (#785)
Update index.md (#785)

I'm the author of the Ionic 2 master course on Udemy. I've changed the URL so that your readers get 50% off the list price ($15 instead of $30). Hope that's ok :)
ionic-team/ionic-site,driftyco/ionic-site,ionic-team/ionic-site,ionic-team/ionic-site,driftyco/ionic-site,driftyco/ionic-site,ionic-team/ionic-site,driftyco/ionic-site,driftyco/ionic-site