Date all press releases / announcments

[jidanni]

From https://github.com/MyEtherWallet/meta/issues/2

[crines]

Definitely agree with this suggestion about dating files and articles, right up at the top of the document, so one can tell if what they are reviewing is older, or newer, than the last reference material they've just looked at. Otherwise your customers will be going around in circles and possibly reversing settings that were already appropriate or will become more confused and frustrated.