Pass circle members feature test

Test was failing for 2 reasons:
1) the submission was not being created successfully because there was
no allow_nil/allow_blank on the submission model validation for
unique track_ids per circle.
2) the dummy user was not eing created successfully because it was
using the same email addresss as the current_user.

Both are fixed now and the test passes. Hurrah for good old fashioned
debugging - discovered the Mac console utility for log files in the
process.
User now have many stems and remixes, not just tracks.

Current_user has been updated to reflect this.
update join circle spec to click form buttons instead of links
create routes for submissions - create and destroy
Create Submissions controller - create, destroy (undo)

create an undo link for the new submissions success flash message.
update the user layout file to render the html of the undo link
properly
add stems as buttons to join circle with - pass the join circle test

hide the buttons unless the current user is not already a member of
the circle.
typo correction on submit, add user name to offcanvas menu title