Adds in-app subject and author links

[JPrevost]

• local_browse feature now uses in_app links instead of external links
  to EDS UI for authors and subjects
• external links are still used when local_browse is not enabled

NOTE: I'm not sure this is actually working as intended as I don't seem to get identical results browsing locally and via the EDS UI options.

HINT: https://mit-bento-staging-pr-182.herokuapp.com/toggle?feature=local_browse

[coveralls]

Coverage remained the same at 100.0% when pulling 7e69fb8 on in_app_subjects_and_authors into 8dd0a87 on master.

[frrrances]

I'm noticing a few things:

• Author search seems to work correctly, but not use the filters to limit format
• Subjects don't seem to be working entirely correctly, though I can't figure out a pattern yet - example that shows results when you click "electronic books" but not when you click "Prefect, Ford -- Fiction" even though 2 of the top 5 results have that subject heading.

I'll keep digging but I think you're right that this needs some tweaking. Since it's a subtle problem, I think we should hold off on merging until we can figure out what's going on, but am happy to discuss if you have your finger on the button...

[JPrevost]

I'm in no rush to merge. We can send this out for more feedback too.

[coveralls]

Coverage remained the same at 100.0% when pulling dc9688b on in_app_subjects_and_authors into 8dd0a87 on master.

[coveralls]

Coverage remained the same at 100.0% when pulling 9b900b1 on in_app_subjects_and_authors into 8dd0a87 on master.

[frrrances]

Subjects looking good now 🌈

[frrrances]

from my perspective, this is all 👍 - though we can wait for feedback from the team.

[coveralls]

Coverage remained the same at 100.0% when pulling 87c25b7 on in_app_subjects_and_authors into 8aa37d1 on master.

[coveralls]

Coverage remained the same at 100.0% when pulling ed0babe on in_app_subjects_and_authors into f480435 on master.