Remove forgotten file
Do not forget to order participations by conf
Add 'header_from_attribute_name' helper function
Work on participant views ('show', 'edit', 'new')
Use empty values for absent request params

Do not expect all params be submitted, use default values if absent.
Use functions to process params for 'edit' action
Use 'attribute_name' instead of 'attribute', etc.

Use "attribute_name" instead of "attribute" and "association_name" instead of "association" where appropriate.
Move common participant form fields to a partial

Move common participant create/update form fields to a partial.
Don't nest talk proposal fields in participations

Do not nest talk proposal fields in participations fields in creating and updating participants.