Want velocity_polyfit to return uncertainties on polynomial fit parameters

[aringlis]

Currently, velocity_polyfit within eitwaveplot.py performs a polynomial fit to the wavefront position data in a given column using numpy.polyfit.

numpy.polyfit returns the best-fit polynomial parameters. Additionally, if full=True is set, it will return the residuals, rank of the Vandermonde Matrix, and the singular values of the Vandermonde Matrix. Want to use this information to determine the uncertainties on the polynomial fit parameters.