Circular Modulus: remove requirement of -540 being the lower limit

Since fmodf(x,360) will return something between -360 to 360 we can
just add 360 to get a positive output instead of adding a finite value
before the modulus.  This should make it take in any valid angle in
degrees and avoids a while loop.
Circular modulus: small tweak for efficiency

Thanks to Kenn for the suggestion
Merge pull request #469 from peabody124/circular_modulus_deg

Circular Modulus: remove requirement of -540 being the lower limit