Code cleanup

[ahstro]

I got all excited and couldn't help myself... This does some general code cleanup/maintenance in preparation for some actual fixes and changes. I think the commit names captured what it does pretty well, but pleonasm is a fun word, so here's a repeat:

• Format code using latest version of elm-format
• Run elm-analyze and fix all errors
• Replace krisajenkins/elm-exts with local code and elm-community/maybe-extra (sorry 😇 )

[ahstro]

Worth noting that the build failed due to an HTTP request failing, not because the code is necessarily broken. I can't trigger rebuilds, so can't make the check succeed, but make exits correctly on my local system.

Error: The following HTTP request failed.
<https://github.com/elm-community/elm-test/zipball/3.1.0/>
FailedConnectionException "github.com" 443