fixes ace editor cutting off viewing code

Jira ticket https://issues.apache.org/jira/browse/COUCHDB-2454
This does work, but I don't much like it... :( When resizing the page, the space between the end of the editor and the right side of the window changes. It's a small detail, but I think it should remain consistent. 

Instead, it might be nicer to set that to a full 100% here, then add 20px right-padding to the #dashboard-content (or an immediate child if it's not easy to do for this page alone).