Fix bug related to new behavior of numpy masked...
Fix bug related to new behavior of numpy masked...

Fix bug related to new behavior of numpy masked arrays. This was
causing the first measurement for each step to non-masked (i.e.,
included as valid data) even though it was invalid.

Also remove deprecated calls to pandas.TimeSeries.

wheeler-microfluidics/dmf-control-board-firmware,wheeler-microfluidics/dmf-control-board-firmware,wheeler-microfluidics/dmf-control-board-firmware,wheeler-microfluidics/dmf-control-board-firmware