Add better info about accommodations to sign-up page

[gonuke]

Best practice in accessibility is to not require people to ask about special accommodations, at least the ones that might be anticipated, but to offer them up a priori:

• lactation (consider timing of breaks)
• hearing impaired???
• vision impaired???
• physical accessibility

Also be sure to include a welcoming invitation to be contacted for other requests:

• make it obvious which individual will receive the message (as opposed to "email host here")