Slight tweaks to fix constraint logic

[colincadams]

Description of the change

Please pardon my terrible javascript 😁 noticed a couple issues while prepping for a demo this morning, two small changes plus accompanying tests:

• includes year in constraint months, so that low coverage for a month doesn't remove that month in every year
• only check statewide incarceration rate when determining constraint months
  • our production data currently produces coverage info for county level data also, which isn't very useful so I may remove it but figured we should protect against this in the frontend anyway

Type of change

• [x] Bug fix (non-breaking change that fixes an issue)

Related issues

follow up to #100

Checklists

Development

These boxes should be checked by the submitter prior to merging:

• [x] Manual testing against realistic data has been performed locally

Code review

These boxes should be checked by reviewers prior to merging:

• [x] This pull request has a descriptive title and information useful to a reviewer
• [x] This pull request has been moved out of a Draft state, has no "Work In Progress" label, and has assigned reviewers
• [x] Potential security implications or infrastructural changes have been considered, if relevant

[nasaownsky]

Yep, I agree with @jessex. Great work, @colincadams!