Determine basic User profile info

[jrrickerson]

Decide what information we want to / need to collect about a user. For instance, we certainly need to get in touch with users if talks are accepted or rejected, so perhaps make email addresses required as usernames.

Other information we might want to collect:

• Github username (for reference to code samples from talks)
• Meetup username
• Whether or not to display email with talk listing
• Display name