colors: use the proper ANSI sequence for 'reset'

The more approprite 'reset' code is \33[0;m which resets all character
attributes to the terminal defaults.

See http://ascii-table.com/ansi-escape-sequences.php for details.

This change fixes the problem of poni leaving the terminal with strange
colours on exit.
Merge branch 'colour-reset' of git://github.com/gergelyerdelyi/poni

* 'colour-reset' of git://github.com/gergelyerdelyi/poni:
  colors: use the proper ANSI sequence for 'reset'