Don't show the top level `options` key for diffs

Summary:
Joel pointed out this was kind of weird, that it was always indented by this
one level. This reduces the indentation and doesn't show that top-level key.

Test Plan:
* Open difftest.html
* before: {F13873}
* after: {F13872}

Reviewers: alex

Reviewed By: alex

CC: alpert

Differential Revision: http://phabricator.khanacademy.org/D7211