def flattr_loader_options(site)
      return if site['flattr_uid'].nil?
      keys = %w[mode https popout uid button language category]
      options = flattr_options(site, nil, keys).delete_if { |_, v| v.to_s.empty? }

      options.map { |k, v| "#{k}=#{ERB::Util.url_encode(v)}" }.join('&')
    end
def flattr_loader_options(site)
      return if site['flattr_uid'].nil?
      keys = %w[mode https popout uid button language category]
      options = flattr_options(site, nil, keys).delete_if { |_, v| v.to_s.empty? }

      options.map { |k, v| "#{k}=#{ERB::Util.url_encode(v)}" }.join('&')
    end
Generates the query string part for the flattr load.js from the
 configurations in _config.yml

   {{ site | flattr_loader_options }}