add a regression test for skyoffset pickling
add a regression test for skyoffset pickling

larrybradley/astropy,pllim/astropy,StuartLittlefair/astropy,larrybradley/astropy,mhvk/astropy,mhvk/astropy,astropy/astropy,mhvk/astropy,lpsinger/astropy,StuartLittlefair/astropy,pllim/astropy,mhvk/astropy,StuartLittlefair/astropy,larrybradley/astropy,astropy/astropy,pllim/astropy,mhvk/astropy,lpsinger/astropy,pllim/astropy,larrybradley/astropy,astropy/astropy,astropy/astropy,lpsinger/astropy,astropy/astropy,lpsinger/astropy,StuartLittlefair/astropy,StuartLittlefair/astropy,lpsinger/astropy,pllim/astropy,larrybradley/astropy