Wrong ELO formula

[RanDumSocks]

https://github.com/weegreenblobbie/rank_photos/blob/a7458e3e20dd559f4f5f74421702e64864a1e604/rank_photos.py#L344-L346

This is the wrong formula, it should be:

 E_a = 1.0 / (1.0 + 10.0 ** ((R_b - R_a) / 400.0)) 
  
 E_b = 1.0 / (1.0 + 10.0 ** ((R_a - R_b) / 400.0))