improvements to lantern friends modal

closes getlantern/lantern#1036

- explicitly mention that lantern connects you to users *up to four degress
  away from you in your social network*
- prompted actions for friend suggestions are now "add" and "dismiss". "friend"
  and "decline" made it seem like it was in response to a friend request, not
  a suggestion.
- show badge with friend suggestion count over lantern friends nav item during
  initial setup