Config for how much book content is saved moved to .env

Please run commands that hit db/seeds with `foreman run`
Use flexmock to mock, fix failing scaffold specs.
Remove stopwords from search queries using RailsNlp.
"Open Book" on search results page links to books#show
Refactor: move stopwords logic to lib/ out of controller.
Merge branch 'remove-stopwords-from-query'