Revert "Uncomment error check"

This reverts commit b0a9e614f45ec6df20d5a17a4eb7500b463d3161.
Revert "Added failing test for loose files being compiled separately"

This reverts commit 660ea3b58857cc43cb26d0ecdd9787880868d24f.
Revert "Changed dummy#assets to render to json any asset"

This reverts commit 1444808f50f104c56c80ad044eb07b55cb5430d4.
Fixed asset compilation test
Redefine sprockets-rails LOOSE_APP_ASSETS constant