failing test case with .html.erb preferred instead of .coffee

[lennart]

This PR shows coffee-rails views not being picked for JS routes when a .html.erb template exists for the same action.

In the comments of the dummy controller are the currently necessary steps (I haven't found explicit documentation about needing to do this!) to make the .coffee file (or .js.coffee) being picked up and served when accessing /site/index.js.

NOTE: the current full test suite fails (even without these changes) since sprockets 4.0 will be installed and it requires a set up manifest.js for the asset pipeline...

[lennart]

since this is no solution for the problem, I would ask how and where this problem should be fixed