Update commonmark.org

[chrisalley]

See @jgm’s response in this similar topic:

Fast away the old year passes

Seems our homepage’s last paragraph is in need of a chronological update. When is the spec final? The current version of the CommonMark spec is complete, and quite robust after a year of public feedback … but not quite final. With your help, we plan to announce a finalized 1.0 spec and test suite in early 2016. <3 http://commonmark.org (Accessed January 16, 2017)