add timestamps columns to tables where missing
Merge pull request #76 from alpha-tango/timestamps

add timestamps columns to tables where missing
update validations on course
validations on assignment
element validations
validations on questions quizzes and answers
Merge pull request #78 from alpha-tango/validations

Validations
add enrollments table model and spec
Various small styling changes

*resize edit and delete buttons for questions/elements to tiny
*change user page to fit with general theme
*edit assignment show page to simplify display
Merge pull request #79 from alpha-tango/restyling

Various small styling changes
restyle edit element
change default ordering of elements
fix columns in assignmnet show
update default scoping
fix course created at view
add feature tests for enrollments
add enrollments to user and course show pages
merge master
Merge pull request #80 from alpha-tango/enrollments

Enrollments
quiz form tests run properly