How to invert pen up/down operations

[willprice]

The instructions on the website explain how to invert the movement of the x/y steppers, but not the pen up/down stepper.

Swapping the defaults of pw_up and pw_down seemed to do the job, i.e.

# Original BrachioGraph kwargs
pw_up=1500
pw_down=1100

# Flipped BrachioGraphs kwargs
pw_up=1100
pw_down=1500

It'd be nice to include this in the documentation. Or perhaps provide a kwarg like reversed that flips everything for you if all your steppers are reversed in the same way.