Adds Searchevent and term

[JPrevost]

Why are these changes being introduced:

• this implements the first two models and will enable the storage of
  the data necessary to get started with this application

Relevant ticket(s):

• https://mitlibraries.atlassian.net/browse/ENGX-232
  https://mitlibraries.atlassian.net/browse/ENGX-233

How does this address that need:

• Rails

Document any side effects to this change:

• some of our typical developer gems, rubocop and annotate were added
• rubocop was used to autoformat everything in the /app and /test
  directories
• adds our standard CI setup
• adds dependabot weekly checks

[jazairi]

This is consistent with my understanding of the most recent version of the class diagram. I suspect we'll want an initialize method on the Term class, but we can add that later if it makes sense when we start to do more with these models.

Thanks for doing all the Rails and CI setup, too; in retrospect, that probably should've been a separate ticket!

[JPrevost]

@jazairi yeah I hadn't decided yet where the logic would live to sort find_or_create a new term to add a new SearchEvent. That could be what you were referring to with the initialize method? Either way, I agree we can add it when we need it (wherever it ends up making sense)