text: Title: How to avoid black padding pixels?
  Body: Thanks for the great work! I have a question about the face detector module.
  The README.md mentions that 
  
  > To avoid deformation, deepface adds black padding pixels according to the target size argument after detection and alignment.
  
  If I don't want any padding pixels, what pre-processing steps should I do? Or is there any requirement on the shape if I want to skip the padding?