Refactoring and simplifying code for nomination (bug 717495)

This is a follow-up of [a previous attempt](https://github.com/mozilla/olympia/commit/1cc89c245f2acc92db59c2280bfe430d2d9f32d3) to fix that bug.
From what I can see, with this type/style of docstring, there's no newline before the closing quotes. (same below)