Hotlinked bio image

this is my first attempt to make https://github.com/mmistakes/minimal-mistakes accept hotlinked images, too. Wanted to try this first only for the bio pic, see how @mmistakes likes it.
I'll wait for any suggestions as to how to make this more elegantly/efficiently, before implementing it likewise for all other image related stuff in https://github.com/mmistakes/minimal-mistakes, as per #26 etc. 

Ps.: @mmistakes still have to figure out an appropriate thank-you shoutout to you for making this awesome template available to everyone. Such great work.