Gracefully handle no-facebook case for people.

- Not all people will have Facebook pages.
- Instead of trying to render a non-existing page,
  we can just tell the user that the person they’re interested in
  has no Facebook page.
refactor: better var/id names
refactor: two less lines
Gracefully handle no-twitter case for people.

- Not all people will have Twitter accounts.
- Tell the user that the person they’re interested 
  in has no Twitter account.
Merge pull request #59 from codeforamerica/frontend/handle-missing-social-accounts

handle missing social accounts for people