Fixing Link to Contributing guide
Fixing Link to Contributing guide

Link was a 404, added missing '/' in url
8thcolor/eurucamp2014-htdsadr,8thcolor/eurucamp2014-htdsadr,8thcolor/eurucamp2014-htdsadr,8thcolor/rubyconfau2015-sadr,8thcolor/rubyconfau2015-sadr,8thcolor/rubyconfau2015-sadr