app/stories/speakers/withdraw_proposal.md
/events/:slug/proposals/:id
As a speaker with a submitted proposal,
If my proposal has NOT yet been accepted,
I want to see a 'Withdraw Proposal' button.
Upon clicking 'Withdraw Proposal'
I want to see an alert box that informs me that withdrawing my proposal
will remove my proposal from consideration and send an email to the event coordinator
So that I must confirm - by clicking 'OK' - that I approve this irreversible action.