Opt out of Turbolinks in non-Alchemy controllers

[dssjoblom]

We are trying to integrate Alchemy into a larger app that doesn't work with Turbolinks. It would be nice if the app could set config.turbolinks.auto_include = false in its configuration files so that Turbolinks is not used by default in controllers. The Alchemy controllers should then explicitly include Turbolinks.

See dssjoblom@f4591cc. I can make a PR for this if you are interested.

[tvdeyen]

Include Turbolinks explicitly in case Alchemy is embedded into a larger application that doesn't work with Turbolinks. The app can then set that Turbolinks is not included in the app controllers.

# config/appplication.rb
config.turbolinks.auto_include = false