Code review edits

- Removes unneeded text in Readme and Installation instructions.
- Quotes strings that were breaking syntax highlighting in
`settings.yml`.
- Incorporates upstream language links settings updates from
https://github.com/codeforamerica/ohana-web-search/commit/b9228db02c7eb7
77f15981eb7f0d40bc32cb21d2
- Incorporates upstream admin site URL updates from
https://github.com/codeforamerica/ohana-web-search/commit/38c1d7ce9d2f9f
6372af9953ce8ad74ba631378d