Convert extra "moveto" coordinates to implicit "lineto" commands

Per the [SVG spec](http://www.w3.org/TR/SVG11/paths.html#PathDataMovetoCommands):

> If a moveto is followed by multiple pairs of coordinates, the
> subsequent pairs are treated as implicit lineto commands. Hence,
> implicit lineto commands will be relative if the moveto is relative,
> and absolute if the moveto is absolute."