Release documentation improvements resulting from the 0.0.6 practice release

See:
 * Original release process ticket #293  
 * Example download links: https://github.com/ClusterHQ/flocker/issues/488#issuecomment-51506871
 * Release branch: https://github.com/ClusterHQ/flocker/compare/release/flocker-0.0
These single back ticks around the curl command don't seem to change the formatting. I think double-backticks were intended.
Single back ticks:

---
![single](https://cloud.githubusercontent.com/assets/797801/3855805/09007410-1eeb-11e4-9b36-43b19731427c.png)
---
Double backticks:

---
![double](https://cloud.githubusercontent.com/assets/797801/3855810/104a7cf2-1eeb-11e4-9a83-85d670350f3b.png)
---
I don't think that this is great either, so perhaps this should be in a separate block like other commands on this page.