Add supporting partners section, revise supporting institutions.
Merge pull request #579 from jcushman/partners4

Add supporting partners section, revise supporting institutions.
Use requests to check iframe-ability.

Fixes #576
Merge pull request #580 from jcushman/dev.requests

Use requests to check iframe-ability.
Added UNC as a partner. Fixes #558
Added Widener Law. Fixes #562
Added SMU as partner. Fixes #570
Merge branch 'dev.logos' into develop
Added note to markup that will let us easily see which mirror
served up the archive.