Feature/stable repo links

Hi @barnabyalter 

All tests are passing here now, but deploying this will require incorporating the companion pull request in the findingaids_ead repo and deleteing/reloading tamwag/tamiment, archives/universityarchives, bhs/brooklynhistory, and nyhs/nyhistory.

I had one question, which I'm including as an inline comment in the code below.

Let me know if you have questions or comments

cc @NYULibraries/finding-aids 
@chrpr I'd prefer something like this for all of the repositories:

```
Given I am on the "fales" stable URL
When I search on the phrase "Postal Art Network"
Then I should see results
```