Adding a link for exporting events.

#2672 
![ical1](https://f.cloud.github.com/assets/1222368/617024/f64da416-ce85-11e2-9f07-5537be31c068.png)
![ical2](https://f.cloud.github.com/assets/1222368/617025/f66b5a42-ce85-11e2-8a43-ac383e8d4756.png)