Attempt to de-flake auto arrange request spec by removing 'fade' class from modal

Previously, it seems like Capybara might've been trying to click 'Auto-Arrange' before it was
fully faded in, causing unexpected results.

Now, modals spawned by backbone for the section arranger don't have the 'fade' class if
the Rails.env is "test", so they should be less flakey in capybara situations.

Additionally this moves a lot of jQuery nonsense I wrote regarding the auto-arrange modal
into more better backboney code.