Clicking on backdrop doesn't close the modal

[jsilvestre]

It cannot work for two reasons:

• the selector is wrong (see https://github.com/cozy/cozy-clearance/blob/master/client/modal.coffee#L18), it should be .modal-backdrop.fade.in
• the .modal-backdrop is behind the actual modal and its backdrop

The fix for the second reason isn't straightforward: if we put the backdrop in front of the modal, clicks on the modal are going to be captured.

[aenario]

This actually makes things easier :

• we listen for clicks on @$el
• we do nothing if event.target.parents('.modal-dialog') an trigger onNo otherwise.

What do you think ? Do you want to include it to the current PR ?

[jsilvestre]

Let me try to fix it before merging, yes (don't merge files neither). Thanks for the tip!