Security update, removal of Devise token auth

# What changed

 * Critical security update for Rails 4. Upgraded to 4.0.3
 * Removed Devise token auth from project. **Yes, I broke the build**. Please see note below.

**It has been a very busy week for me outside of the Farmbot project so I have not been able to do many code commits. If someone has the time to get the test suite to pass using a custom (secure) token auth strategy it would be greatly appreciated. [A good starting point can be found here](https://gist.github.com/josevalim/fb706b1e933ef01e4fb6).** Otherwise, I will start working on it next week after deploying the new OpenFarm server.