add hide_related option

lib/auto_html/youtube.rb

@@ -5,9 +5,10 @@ module AutoHtml
   class YouTube
     include TagHelper
 
-    def initialize(width: 420, height: 315)
+    def initialize(width: 420, height: 315, hide_related: false)
       @width = width
       @height = height
+      @hide_related = hide_related
     end
 
     def call(text)
@@ -37,6 +38,9 @@ def youtube_pattern
 
     def iframe_attributes(youtube_id)
       src = "//www.youtube.com/embed/#{youtube_id}"
+      params = []
+      params << "rel=0" if @hide_related
+      src += "?#{params.join '&'}" unless params.empty?
       {
         width: @width,
         height: @height,

spec/auto_html/youtube_spec.rb

@@ -45,4 +45,10 @@
     result = subject.call('www.youtube.com/watch?v=t7NdBIA4zJg')
     expect(result).to eq '<div class="video youtube"><iframe width="420" height="315" src="//www.youtube.com/embed/t7NdBIA4zJg" frameborder="0" allowfullscreen="yes"></iframe></div>'
   end
+
+  it 'transforms url with hide_related options' do
+    filter = described_class.new(hide_related: true)
+    result = filter.call('www.youtube.com/watch?v=t7NdBIA4zJg')
+    expect(result).to eq '<div class="video youtube"><iframe width="420" height="315" src="//www.youtube.com/embed/t7NdBIA4zJg?rel=0" frameborder="0" allowfullscreen="yes"></iframe></div>'
+  end
 end