function coerce(attr, dflt) {
        return Lib.coerce(containerIn, containerOut, attributes, attr, dflt);
    }
options: object containing:

 letter: 'a' or 'b'
 title: name of the axis (ie 'Colorbar') to go in default title
 name: axis object name (ie 'xaxis') if one should be stored
 font: the default font to inherit
 outerTicks: boolean, should ticks default to outside?
 showGrid: boolean, should gridlines be shown by default?
 data: the plot data to use in choosing auto type
 bgColor: the plot background color, to calculate default gridline colors