Pygments offers great styles and in dark terminals the default is unsatisfactory.
Use two new env variables BASH_IT_CLESS_STYLE and BASH_IT_CCAT_STYLE to select pygment themes.
Availables styles can be listes using pygmentize -L styles
When pygmentize is not installed, the functions less/cat are not
defined, the native commands will be used instead. Also removed the
error message that was shown when the command was not found.
Using `command -v` instead of `which` to check for the existence of the
executable - this works better as it does not print an error message if
the executable is not found.
markusdd
Stéphane Adjemian (Charybdis)
Nils Winkler
Miguel Morales