Update CodeMirror submodule.

Move to new repository location on Github.  Update to version 2.35.
Fix patch generation.

With the CodeMirror update, the CodeMirror object no longer
edits the text value in-place.  So, we must sync from the content of the editor to our buffers before generating patches.
Fix local patch save.

The BlobBuilder has been deprecated in HTML5.  Blob is used instead.
Add karma test configuration.

Also fix failing tests.
Run karma instead of phantomjs in alltests.py.
Add istanbul/karma coverage.
Update codemirror to 3.14.
Merge branch 'codemirror-update'