def avatar_url(size)
      valid_sizes = [128, 73, 48, 24]
      size = valid_sizes.min { |a,b| (size-a).abs <=> (size-b).abs }
      "https://s3.amazonaws.com/uifaces/faces/twitter/#{username}/#{size}.jpg"
    end
def avatar_url(size)
      valid_sizes = [128, 73, 48, 24]
      size = valid_sizes.min { |a,b| (size-a).abs <=> (size-b).abs }
      "https://s3.amazonaws.com/uifaces/faces/twitter/#{username}/#{size}.jpg"
    end
Public: FakeFriend.new(username)
 Creates a FakeFriend object with attributes fetched from
 the user listing defined in users.yml and accesses via FakeFriend.all

 username  - String - a Twitter username found in the user listing

 Examples

   FakeFriend.new('idiot')
   # => #<FakeFriend:0x00000101348a80 @username="idiot"...>

 Returns a FakeFriend object with attributes populated from FakeFriend.all
 Public: returns a user's uiFaces url in the closest available size

 size  - Integer - the requested image size (length = width), in pixels

 Returns a string with the appropriate url.