Removed some dead code
Removed some dead code

- removed some unused code
- improved efficiency of cut_levels() method by eliminating one clip()
  operation

pllim/ginga,ejeschke/ginga,naojsoft/ginga,ejeschke/ginga,pllim/ginga,naojsoft/ginga,ejeschke/ginga,naojsoft/ginga,pllim/ginga