turning rotary encoder fast causes failure

[mrjones-plip]

Steps to reproduce:

1. turn rotary encoder fast, eg 2+ clicks a second

expected: volume goes up quickly, directly corresponding to each click
actual: volume doesn't go up, sometimes even goes down one or two

work around: if you turn the rotary encoder slowly it seems to consistently work.

testing:

• for comparison, simple.rotary.test.py seems to work really well. However the full app as seen in cattrotar.py has the problem as described above.
• different rotary encoders and different jumper cables have been tested - this doesn't fix the problem