CodeMirror Line Numbers are Offset in Admin Dashboard

[elikir]

I've been trying to integrate DBTemplates into my site and have run into a bug when using CodeMirror where the first line of code starts on what appears to be line 3, but it's just the div containing the line numbers being pushed down for some reason. Changing the width of the iframe from 100% to 90% seems to be a viable fix, but I'd be very surprised if this isn't something that's been found before.

I've put a screenshot of what we're seeing down below

[mpasternak]

I guess we could merge it into codebase as it does not seem to affect non-CodeMirror users. Would you like to submit a pull request?