def remove_site (site)
      return nil unless @sites.map{|s| s[:name]}.include? site
      @sites.reject!{|s| s[:name] == site}
      @need_to_update = true
    end
def remove_site (site)
      return nil unless @sites.map{|s| s[:name]}.include? site
      @sites.reject!{|s| s[:name] == site}
      @need_to_update = true
    end
Remove this user from a site

 @param site[String] the name of the site

 @return [void]