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
Restrict FriendlyID to 4.x branch

For Rails3 compatibilty it's best to use the 4.x stable branch of
FriendlyId. FriendlyId5 is only compatible with Rails4+.

https://github.com/norman/friendly_id/blob/master/README.md