Rails 4.0 - bring back in-place editing support for collection associations 

This PR is related to
https://github.com/rails/rails/issues/12140, https://github.com/rails/rails/issues/12213, https://github.com/rails/rails/commit/1a40be02113287d9a003f8224e91b9f623857f4b and https://github.com/rails/rails/pull/12227
Since personally I'm very unhappy with the way the resolution of these issues is heading, and I thing it's killing the fun in Rails and forces me to write awkward code - here goes my offer