Strong params modification

Made changes to whitelist params hash using strong_parameters. Ran rake training with no failures (RAILSGOAT_MAINTAINER set) and all 14 failures (RAILSGOAT_MAINTAINER unset).

I left Rails at version 3 since that is what the Gemfile had, along with a don't change comment. It is easy to move to Rails 4; remove the strong_parameter gem and config/initializers/strong_parameters.rb.

Let me know if there is any change you want made.