Improve warning for time_resolutions below 10us
Improve warning for time_resolutions below 10us

pllim/astropy,dhomeier/astropy,lpsinger/astropy,saimn/astropy,saimn/astropy,lpsinger/astropy,dhomeier/astropy,saimn/astropy,larrybradley/astropy,astropy/astropy,lpsinger/astropy,StuartLittlefair/astropy,astropy/astropy,lpsinger/astropy,aleksandr-bakanov/astropy,aleksandr-bakanov/astropy,dhomeier/astropy,StuartLittlefair/astropy,saimn/astropy,mhvk/astropy,larrybradley/astropy,larrybradley/astropy,pllim/astropy,StuartLittlefair/astropy,StuartLittlefair/astropy,mhvk/astropy,saimn/astropy,dhomeier/astropy,astropy/astropy,larrybradley/astropy,mhvk/astropy,mhvk/astropy,StuartLittlefair/astropy,lpsinger/astropy,dhomeier/astropy,astropy/astropy,astropy/astropy,mhvk/astropy,pllim/astropy,aleksandr-bakanov/astropy,larrybradley/astropy,pllim/astropy,aleksandr-bakanov/astropy,pllim/astropy