Added Copenhagen workshop

@github/training-team, I can't get this to order correctly on the site, so that the May event is listed above this Copenhagen June event. Do I not know my alphabet? 

![screen shot 2013-05-14 at 2 14 00 pm](https://f.cloud.github.com/assets/3474911/504000/6a0062d4-bcdb-11e2-82e4-a41b03c0a7d3.png)

I thought the numbers would do it: "2013-06" after "2013-05", but that didn't do it. Or "workshop" after "peter", but that didn't do it either. 

What am I doing wrong??