E1476 adding the 4 features
adding the deleted schema.rb in original form

had fixed the node.rgt error when running locally. it had got deleted by mistake so restoring it to its original state.
restoring the sign_up_sheet_controller 

this had got deleted as locally we have commented the require graphviz_dot file and did not want to commit it. we are restoring it now to original state.
Remove graphviz from the sign_up_sheet_controller
Add the database.yml.example back
Remove MiniTest, as it is no longer used
Merge branch 'rails4' into e1476

Conflicts:
	app/views/student_review/_responses.html.erb
	app/views/student_review/_set_dynamic_review.html.erb
	app/views/student_review/_set_student_review.html.erb