doplot for horizontal boxes (internal bxp helper function) assumes that
it will be passed an even number of positional arguments which it swaps
pair-wise.  The code to draw the fliers also passes in a format string
which breaks the assumption.

 - re-worked how `bxp` deals with the `sym` input
 - minor pep8

If the user passes is the string 'ro' assume they want filled circles.
This is also the old behavior.

 changed labeling in cbook.box_plotstats to start at 1 to
 maintain back compatibility