Changing associations to reflect dependencies

Updating associations to remove the event_id from the score_template
model so that there can only be one score template per event (User story
#8). I also updated the associations so that they have dependencies
specifying removal when their "parent" association is destroyed.
Migration and association

Migrating the database to remove the event id from within the score
template table so that an event only has one score template as the model
suggests (User story 8). In addition, I reflected those changes in the
model as well as in the "form" view as I removed the hidden event_id
field.