doc str cleanup
BF: Window background color- eyelink cal graphics
Changed eyelink config default setting
Merge branch 'master' of git://github.com/psychopy/psychopy
BF: FutureWarning fixed

When running python 2.7.7 I was getting the following warning from
shape.py:

> FutureWarning: comparison to `None` will result in an
> elementwise object comparison in the future.

Fixed by changing "!=None to "is not None".
ENH: gcCursor eye tracker demo

Now by default no eye tracker config is enabled in iohub_config for
experiment. If demo is run, error dialog is displayed. User must
explicitly uncomment the eye tracker config for the ET hardware being
used to run the demo.
BF: psychopy.iohub.client.Keyboard clearEvents

Was clearing iohub server event buffer but not local Keyboard device
event buffer. Now it does both.

Bug introduced in 1.81.
BF: iohub selectTracker demo

Was broken due to keyboard device event changes. Now is fixed and also
updated to use new Keyboard device API.
BF: validation eye tracker demo

win arg was missing, causing demo to fail.
BF: removed prints
BF: iohub eye tracker independent validation

also requires version 1.8 of six.py
Merge pull request #733 from isolver/master

Mainly BF for eyelink calibration screen background color