code: public String buildProfileImageUrl(String id) {
  		StringBuilder builder = new StringBuilder();
  		builder.append("http://graph.facebook.com/");
  		builder.append(id);
  		builder.append("/picture?type=large");
  		return builder.toString();
  	}
docs: Constructs the URL to access the FB graph API and retrieve a profile image for the
  user with the given facebook id.
  @param id
  @return