Share rendering code for embedded votes and vote detail

Summary:
We have two separate pieces of rendering code and both are pretty ugly. Move them toward being more reasonable.

This could no doubt be improved:

• Getting a text style which was readable on both the dark and light bars was hard, maybe we should change the colors or maybe I am just bad.
• Could probably benefit from actual competent design in general.
• JS magic is temporarily ineffective, I'll restore that in the future.
• Embed style is a little funky (margin/centering).
• Could use a little cleanup.

Test Plan:
{F50226}
{F50227}
{F50228}

Reviewers: chad, btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D6465