zernike.py - committed the n00b error of using a mutable object as a default value. fix to use None as default and add necessary code to deal with that. add missing docstring as well
zernike.py - committed the n00b error of using a mutable object as a default value. fix to use None as default and add necessary code to deal with that. add missing docstring as well

MMTObservatory/mmtwfs