use supported version of gem state_machine

[compwron]

I did some looking around, and here are my notes so far:
The current version we are using is the specific git commit seuros/state_machine@95ba53f The arooo commit message is "Switch to less abanadoned version of state_machine gem - But this is only a step toward actually being on the maintained version, but can't do that till we get on Rails 4.2"

I read the thread on pluginaweek/state_machine#310 (the original, now unmaintained gem) and it sounds like https://github.com/state-machines/state_machines (maintained by sauros) is the current most maintained fork. I tried all the versions published at https://rubygems.org/gems/state_machines/versions but I get the error ERROR: null value in column "state" violates not-null constraint in all our tests.

I'm not yet confident whether this is a real problem or just a problem with test setup- in order to figure this out I'll

1. start up the server and do some manual testing locally
2. check the data in prod to make sure we don't have null status column values

[compwron]

There are no users with empty state in prod

Loading production environment (Rails 4.2.11.1)
irb(main):001:0> User.where(state: nil)
=> #<ActiveRecord::Relation []>