add mentions of the different placeholders possible for gravatar urls, mentionning the new %{email}
add mentions of the different placeholders possible for gravatar urls, mentionning the new %{email}

8thcolor/rubyconfau2015-sadr,8thcolor/rubyconfau2015-sadr,8thcolor/eurucamp2014-htdsadr,8thcolor/rubyconfau2015-sadr,8thcolor/eurucamp2014-htdsadr,8thcolor/eurucamp2014-htdsadr