ENH: new Keyboard + events working on Windows

The new iohub Keyboard device and events are now working on windows.
keyboard_event.key maps to what  psychpy.event.key returns on Windows
with a latin-1 char set.

I have updated the iohub keyboard demo (now at
demos.coder.iohub.keyboard.py) to display both the .key and .char values
from a keyboard event. The value returned by event.getKeys() is also
displayed, and a warning is shown if the two key values do not match.

Testing help on Windows wit other char sets etc. would really help.

Other OS's need to be updated next; Linux and OSX currently will not
work at all.

Will first do Linux.

Will do OS X last as part of OS X keyboard rewrite.