Added bullet point about code formatters to code style guide
Added bullet point about code formatters to code style guide

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