Major changes:
- if the primary star and secondary star have equally good orbital coverage, now both stars' orbital elements may be solved for at once using the parameter star = "both".
- if the user thinks the orbit is circular, they can use the parameter zeroEcc = True, which holds eccentricity and argument of periastron at 0.
Minor changes:
- fixed a bug that sometimes made the RV curve jagged for the phase plots
- fixed a bug with the returned uncertainty for the argument of periastron for the star = "secondary" application.