implemented _render_icon() on barplot
implemented _render_icon() on barplot

tommy-u/chaco,burnpanck/chaco,burnpanck/chaco,tommy-u/chaco,ContinuumIO/chaco,burnpanck/chaco,ContinuumIO/chaco,tommy-u/chaco,ContinuumIO/chaco,ContinuumIO/chaco