Muck around with Diviner method documentation display

Summary:
Ref T988. Not sure about this, feel free to push back or tweak it or whatever, but I want to reduce the amount of meta-text in the method documentation. Primarily this:

• Shortens "From parent implementation in ClassName:" to "ClassName".
• Tries to tweak the styles a bit so that it's relatively obvious what that means (hopefully?).
• Fixes an issue with tasks where some methods could be ignored.

Test Plan: {F57565}

Reviewers: chad

Reviewed By: chad

CC: aran

Maniphest Tasks: T988

Differential Revision: https://secure.phabricator.com/D6911