[dist] Update README for latest release

+ Clean up a couple of typos and trailing spaces.
[webui] Improvements in comment display

 * @user in the body is now a link
 * Use user_with_realname_and_icon to display the author
 * Mails are sent with multipart in plain text and html
 * Layout for the html version of the mails
[webui] update to codemirror 4.2