module for indexed colors used by XTerm

 Convert::Color::XTerm is subclass of Convert::Color::RGB8 and provides lookup
 of the colors that xterm uses by default. Note that the module is not
 intelligent enough to actually parse the XTerm configuration on a machine,
 nor to query a running terminal for its actual colors. It simply implements
 the colors that are present as defaults in the XTerm source code.
 .
 It implements the complete 256-color model in XTerm.