Add to Favourites with One Click

I'm going to try to update fanconcert more often with small updates, like once per week. Now that I'm an independent consultant for Ruby on Rails, unfortunately I'm a lot shorter on free time for fanconcert.

The first example of a small update this week: you can now add artists to your Favourites from the artist page with *one click*. You can do the same things with releases (Release Collection), concerts (Watched Concerts) and users (Friends).