Add asdf/version info to docs/install.rst
Add asdf/version info to docs/install.rst

aleksandr-bakanov/astropy,mhvk/astropy,saimn/astropy,pllim/astropy,dhomeier/astropy,astropy/astropy,bsipocz/astropy,larrybradley/astropy,larrybradley/astropy,saimn/astropy,StuartLittlefair/astropy,astropy/astropy,dhomeier/astropy,StuartLittlefair/astropy,bsipocz/astropy,aleksandr-bakanov/astropy,astropy/astropy,lpsinger/astropy,lpsinger/astropy,pllim/astropy,bsipocz/astropy,aleksandr-bakanov/astropy,astropy/astropy,StuartLittlefair/astropy,dhomeier/astropy,MSeifert04/astropy,stargaser/astropy,dhomeier/astropy,lpsinger/astropy,mhvk/astropy,mhvk/astropy,aleksandr-bakanov/astropy,saimn/astropy,MSeifert04/astropy,StuartLittlefair/astropy,saimn/astropy,stargaser/astropy,pllim/astropy,StuartLittlefair/astropy,larrybradley/astropy,pllim/astropy,larrybradley/astropy,lpsinger/astropy,astropy/astropy,larrybradley/astropy,mhvk/astropy,bsipocz/astropy,dhomeier/astropy,mhvk/astropy,stargaser/astropy,MSeifert04/astropy,MSeifert04/astropy,pllim/astropy,saimn/astropy,lpsinger/astropy,stargaser/astropy