Adding information and contact form for upcoming captions changes

This makes changes to the captions documentation that adds the caption change form, and some more clear information about what to expect with the new captions. This is what the form looks like: http://cl.ly/image/01452S0H2D2L. I would like to wait for this to be live in the documentation until the blog post is live as well.
Could it make sense to break this into a few paragraphs, so make sure they get the info at the end of this paragraph?