Add feedback to rejection emails

The issue names no files, tests, or entry points; begin by locating the rejection-email workflow in the Rails application and reviewing how proposal outcomes are represented. Done would require an agreed feedback model and supportive rejection emails that close the loop, but the issue does not define the implementation or acceptance tests.

Having been on the review committee for RailsConf 2016, and been a submitter for many before it, I think constructive feedback in the rejection email would alleviate the anxiety of the unknown and could encourage speakers to submit again in the future.

I spoke with an individual last year at RailsConf 2016 that didn't know why his proposal was rejected; He didn't know if it was totally off or close. I logged in, and told him he was close, but it just didn't make it for the year. Due to that he resubmitted the talk this year and was accepted. He told me that he might not have, had he not known it was close.

I can speak from experience: I've been rejected, but not sure if it was due to something I could address in the future, or it simply didn't win out over other talks. You're left "in the dark."

Whatever solution is found, I feel it needs to:

• Have little impact on the review committee's process
• Provide constructive and direct feedback
• Be encouraging and supportive and not callus and blunt
• Close the loop on the process and not leave a vague sense that the door is still open for the current event

After speaking with @mghaught it appears that many/most talks fall into one of a few buckets:

• Talk lacks clear attendee value
• Talk is vague or too broad
• Talk topic is overdone
• Talk topic was out of alignment with the goals of the event
• Talk was a runner up, but another talk won out
• (likely a few more)

As we all know, putting a talk together can be time consuming and scary. Given feedback can make the experience encouraging and empowering. That's the ultimate goal.

(I'll include implementation thoughts below)