Update parenthetical about graphviz and tweak spacing [skip travis]
Update parenthetical about graphviz and tweak spacing [skip travis]

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