Make edit and destroy links more prominent

Probably unnecessary noise, but just to have someone with a more aesthetic understanding than me look at what it does. Ping @lislis @katrin-k: maybe? It adds Bootstrap's `btn btn-default`.

![bildschirmfoto vom 2014-03-28 08 53 36](https://cloud.githubusercontent.com/assets/164400/2547378/098a1d40-b650-11e3-970e-79b4d7740052.png)
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![bildschirmfoto vom 2014-03-28 08 54 34](https://cloud.githubusercontent.com/assets/164400/2547379/0b8b8052-b650-11e3-9265-917f5816aacb.png)