factoring LinePlot's render methods out into classmethods (since they are stateless anyway), so they can be used by other renderers that are not direct subclasses.  also, fixing _render_hold and _render_connected_hold to behave properly when in a vertical orientation.
factoring LinePlot's render methods out into classmethods (since they are stateless anyway), so they can be used by other renderers that are not direct subclasses.  also, fixing _render_hold and _render_connected_hold to behave properly when in a vertical orientation.

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