Fix advertisements.
Fix advertisements.

Signed-off-by: cathywupei <cathywupei@gmail.com>
Fix functionality of advertising for teammates.
This commit also includes the new assignment_controller written by
Hao Liu.  This seems to be redundant, because the previous commit
to master already contained the new assignment_controller.
Merge branch 'master' of https://github.com/expertiza/expertiza

Conflicts:
	app/models/assignment.rb
	app/views/sign_up_sheet/_available_slots.html.erb
	app/views/sign_up_sheet/_micropayment.html.erb
	app/views/sign_up_sheet/_num_of_choosers.html.erb