add alt text to release logo
add alt text to release logo

Closes #95

LestaD/iojs.org-website,benjamingr/website,phillipj/iojs.org,iojs-es/website,lucasconstantino/iojs.org,krahman/website,mikeal/iojs.org,stojanovic/iojs-website,nodejs/iojs.org,Fishrock123/iojs.org,krahman/website,rogeriopvl/website,ruiquelhas/website,marocchino/iojs.org,iojs-es/website,Wirachmat/iojs.org,appleboy/website,stojanovic/iojs-website,rstacruz/website,diagramatics/iojs.org,phillipj/iojs.org,rstacruz/website,marocchino/iojs.org,diagramatics/iojs.org,benjamingr/website,deliciousinsights/iojs-website,ruiquelhas/nodejs-website,Wirachmat/iojs.org,deliciousinsights/iojs-website,LestaD/iojs.org-website,laosb/iojs.github.io,mikeal/iojs.org,nodejs/iojs.org,lucasconstantino/iojs.org,Fishrock123/iojs.org