Rails 4.0.x for good

[related #766]

After cherry-picking and working in a few commits, master is pretty close to rails 4.0.x ..

In this PR, (every task in a different commit) :
- up `rails` `sass-rails` `coffee-rails`, and remove `strong_parameters`(part of rails itself now)
- Use new configs, pretty much replace `whiny_nils` with `eager_load`
- Fix one last test, that now raise a `TypeError`

review @dwradcliffe @sferik 
cc @georgedrummond