Add support for strong_parameters

[bensie]

Don't set attr_accessible if ActiveModel::ForbiddenAttributesProtection is mixed in to the class.

strong_parameters is available as a gem now, but will be the default in Rails 4.

[mceachen]

I don't have any context for this functionality. Does it make sense to add a test related to this change?

[bensie]

Understandable. I didn't want to introduce a dev dependency without first getting your approval, but am happy to add a test for it if that's ok. Alternatively, you could add another Gemfile to Travis so it gets tested against Rails master, which uses strong parameters by default.

From what I could tell that attr_accessible wasn't tested either, was hard to tell if it is even necessary.