Revert "Revert "Considering fixtures harmful""

This reverts commit e2c4a582e9e86f6c718b57e75f8c01cb1c89a838.
Fixing tests broken by validations
Add detention population test data

call using rake db:reset and rake db:populate
Add HAML to gem file
Add SASS reset.css.sass
Add image assets
Remove presence of date, time validation

Detentions can exist without having been set a time or date
Add detention css, replacing scaffolds css
Add methods in model to get detentions for pen and index
Add detentions index