Allow for editing document's privacy

- Add PUT to allowed verbs in document resource
- Merge existing raw data with updated data to avoid overwriting fields
 in a map.
- Use prepared query since I couldn't find how to update a list at a
 given index using hayt (waiting to hear from Max Penet about this)

Fixes #544 

Viewing: 
![image](https://cloud.githubusercontent.com/assets/2522010/5458822/bb6589c6-8555-11e4-806d-fe8f88326698.png)

Editing:
![image](https://cloud.githubusercontent.com/assets/2522010/5458810/a60cbda6-8555-11e4-910d-26755868a824.png)


Doing it this way will break if the URL becomes longer or shorter for any reason. We do the ```(str/split uri #"/")``` in a few places and it makes me a bit nervous. Even doing ```(let [file_name (last (str/split uri #"/"))] ...)``` would be more robust here, but I think we need to look at some general URL parsing things. wdyt?