bug fixes: not printing key/mouse events

also redid startTime as a proper dict
added check if the hdf5 file exists or opens
uh. fixing a silly mistake
to open an hdf5 file and print out the mean gaze xy

To test which version of iohub is being used.
added args to deal with changes of iohub coordinate system

iohub changed the screen coordination system from top-left origin to
center-origin. We have some data before and most data after the shift.

wrote getMeanGaze to see which hdf5 data file is centered and which
ones have top-left origins.

added -o for the origin (default center) and -m for monitor size