text: Title: EELS remove background doesn't work
  Body: Hi.
  
  I want to remove EELS SI background using s.remove_background with fixed energy window.
  
  A "interactive" option works well. (Setting energy window manually)
  
  ```highlossalign.remove_background(background_type = "Power law", zero_fill=True, fast=True)```
  
  But when I set the energy window, It cannot remove background
  
  ```highlossalign.remove_background(signal_range=(825., 849.), background_type = "Power law", zero_fill=True, fast=True)```
  (energy size(channel): 2048, offset 800eV)
  
  How can I solve removing background without setting manually?