Get rid of the deprecated appraisal rake tasks in favor of running
appraisal directly. To run the whole suite, we can run
`bundle exec appraisal rake`.
I also went ahead and updated all the gemfiles.
* support latest Ruby 2.1
* support latest Ruby 2.2
* support latest Rails 4.2
* drop testing of Ruby 2.0
* drop testing of Rails 4.0
* fix JRuby support