force api routes to JSON

Signed-off-by: Graham Ballantyne <grahamb@sfu.ca>
not all routes require authentication

Signed-off-by: Graham Ballantyne <grahamb@sfu.ca>
remove unused require statements
switch from render :text to render :json
add 404s where appropriate
allow unrestricted access to /users/:id/terms (only)
downcase the sis_id, just in case
remove requires_auth_token? method
return to simple api_request? method

always return true