Added documentation page for I/O registry to front page.
Added documentation page for I/O registry to front page.

joergdietrich/astropy,AustereCuriosity/astropy,saimn/astropy,joergdietrich/astropy,aleksandr-bakanov/astropy,saimn/astropy,lpsinger/astropy,dhomeier/astropy,lpsinger/astropy,StuartLittlefair/astropy,stargaser/astropy,saimn/astropy,AustereCuriosity/astropy,funbaker/astropy,joergdietrich/astropy,dhomeier/astropy,aleksandr-bakanov/astropy,stargaser/astropy,StuartLittlefair/astropy,funbaker/astropy,tbabej/astropy,joergdietrich/astropy,astropy/astropy,pllim/astropy,funbaker/astropy,DougBurke/astropy,bsipocz/astropy,StuartLittlefair/astropy,pllim/astropy,larrybradley/astropy,DougBurke/astropy,MSeifert04/astropy,dhomeier/astropy,tbabej/astropy,astropy/astropy,mhvk/astropy,astropy/astropy,larrybradley/astropy,stargaser/astropy,mhvk/astropy,mhvk/astropy,lpsinger/astropy,mhvk/astropy,kelle/astropy,pllim/astropy,MSeifert04/astropy,StuartLittlefair/astropy,aleksandr-bakanov/astropy,stargaser/astropy,kelle/astropy,larrybradley/astropy,AustereCuriosity/astropy,astropy/astropy,tbabej/astropy,kelle/astropy,pllim/astropy,tbabej/astropy,aleksandr-bakanov/astropy,mhvk/astropy,saimn/astropy,AustereCuriosity/astropy,bsipocz/astropy,dhomeier/astropy,DougBurke/astropy,MSeifert04/astropy,AustereCuriosity/astropy,kelle/astropy,funbaker/astropy,lpsinger/astropy,astropy/astropy,pllim/astropy,larrybradley/astropy,saimn/astropy,larrybradley/astropy,lpsinger/astropy,tbabej/astropy,joergdietrich/astropy,MSeifert04/astropy,bsipocz/astropy,kelle/astropy,DougBurke/astropy,dhomeier/astropy,StuartLittlefair/astropy,bsipocz/astropy