improve SED mul & div unit tests to check on redshifted SEDs
(#596)
unit tests for SED withFlux, withFluxDensity, and withMagnitude for redshifted SEDs
(#596)
uncomment SED tests
(#596)
fix rest/obs frame SED transformation bug and forbid SED addition/subtraction for unequal redshifts
(#596)
add redshifts to more SED unit tests
(#596)
SED unit tests with and without redshifting
(#596)
Merge pull request #597 from GalSim-developers/#596

#596 SED.withFlux bug