ENH: ioHub Serial device custom event parsers

User can write a function that will be used by the iohub Serial device
to monitor the serial rx stream and generate Serial device events.

See the customparser.py demo script and associated parseserial.py
script, which contains the example custom parsing function.
Merge branch 'master' of git://github.com/psychopy/psychopy
MISC: iohub cleanup
ENH: ioHub Serial device

1) Added extra device config options: bytesize,parity, stopbits

2) When using a custom parser function, the event_parser.parser_function
key can have a value of the function object itself, or a string giving
the module.function path to the function.
3) Updated customparser demo.
BF: noAudio, fps, dropping video frames when needed

Still maybe issue in terms of first couple frames of video being dropped
sometimes so that video is in sync with audio time base.
Merge pull request #718 from isolver/master

MovieStim2 BF + iohub Serial device custom event parser support.