Update to use bengott:avatar package for user avatars

There will likely be more changes coming soon, but this gets Telescope up to speed for now...

@SachaG: I didn't change any of the scss/css in telescope-theme-base and telescope-theme-hubble -- I'll let you do that. Everything renders fine as is, but you may want to clean up some unused styles.

I don't think anybody is depending on that function anyway. It can probably be removed soon.