I consolidated all the development dependencies in the gemspec,
then ran `bundle update` and `appraisal install`.
I also got rid of unnecessary version constraints (I would rather just
the latest versions of things in development, and we can always add
constraints later if necessary), and removed the jruby-specific gems
since we aren't testing on jruby anymore.
Get rid of the deprecated appraisal rake tasks in favor of running
appraisal directly with `bundle exec appraisal rake`.
I also went ahead and updated all the gemfiles.
* Appraise with Rails 5.2
* Drop specific tiny versions for Ruby
This will reduce churn on this file as we try to keep up to date with
TEENY Ruby releases.
Travis installs Ruby via rvm with the --fuzzy flag. They also keep up to
date with the latest releases, so --fuzzy will likely always give us the
latest TEENY release.
