The spell checking doesn't work well, so removing

I'll try to restore some spell checking in future, but the
native hunspell libraries are causing travis errors and it looks like it
will be a complex issue to get them properly deployed on heroku. I
don't think it's working with current deploys.
Merge branch 'remove-hunspell'
Commit .env because it makes sense to have it in dev and test environments
Remove unneeded gems and upgrade some others
Fixing spelling mistake
Include gem that the activeadmin gem needs
Use a content_tag helper for category.description

In category#show the app would throw a NoMethodError on categories with
nil descriptions (this is from db/seeds.rb).  We may also want to add
some example descriptions to the seeds.rb file.