getkey and explicit new xy

[jkrauska]

• Uses getkey instead of getchar to allow for arrow keys
• sends new x and y coords to xy function to use steps (using self was calculating length 0)

[jkrauska]

@evildmp Any interest in this?

[evildmp]

I like the idea, but is there a way to prevent this from happening when a key is held down?

>>> bg.drive_xy()
X:-10.0, Y:7.0
PW1:1999, PW2:1393
^[[D^[[BX:-11.0, Y:7.0
^[[CPW1:1986, PW2:1293
^[[C^[[C^[[C^[[CX:-10.0, Y:7.0

It happens already with the a/s/k/l controls, but it's more obtrusive as above.

Also, the drive methods should be documented in /docs/reference/brachiograph.rst.