Removed (dead) link to (nonexistent?) Meetup group

The link is dead, no relevant group seems to exist on the Stockholm (at least there are [no search results](http://www.meetup.com/find/?allMeetups=true&keywords=julia&radius=100&userFreeform=stockholm&gcResults=Stockholm%2C+Sweden%3ASE%3Anull%3Anull%3AStockholm%3Anull%3Anull%3A59.32893000000001%3A18.064910000000054&sort=default) for "Julia" within 100 miles of Stockholm...) and [this post on the Julia Users mailing list](https://groups.google.com/forum/?fromgroups=#!topic/julia-users/V6aLwuqMPaI) doesn't seem to trigger any response =(