2160 string edit

Basically the follow-up to https://github.com/apache/couchdb/pull/251
The hidden lines of the map function were mean, but are fixed. I put CSP into a separate PR (it applies even now on master). Finally the "you've edited the page" is fixed. New one on apache:master
I have several points here:

 - `this.$("#editor-container")[0].offsetTop`: you can use jquery here: `this.$("#editor-container").offset().top`
 - can we split this into two lines for a better readability, like:

```javascript
var positionFromTop = ...
this.$("button...
```
- I am not sure what the `2` is? is it a border or padding?