Fix readme.html

 - Restore deleted <html> opening tag and add lang attribute

 - Add UTF-8 charset declaration

 - Move robots meta tag just below the title tag to make it more visible.

 - Fix typo on "its awesome features"

 - Restore "em" dashes: the first one had been deleted without its closing
   counterpart, and the other had been replaced by a hyphen. The em dash
   is a valid typographic character, see its uses at http://en.wikipedia.org/wiki/Dash#Em_dash