Hi!

Thanks for this great gem!

The following test should succeed, but it doesn't. Instead of #main-bar the output contains only #main. One can use this test to implement the feature. Unfortunately my C skills are kind of rusty.

class HTMLTOCRenderTest < Redcarpet::TestCase
  ...
  def test_converting_ampersand_correctly
    markdown = "# Main & Headline"
    output = render(markdown)
    assert output.match("<a href=\"#main-bar\">Main & Headline</a>")
  end
end

Would be great!
Best regards,
Lukas