Feature render tag

[hieuvuvan]

• port render tag from ruby implementation. Render tag like include tag but more strict in term scope. for more detail here https://shopify.github.io/liquid/tags/template#render
• this PR include extra feature: the ability to disable tags. for example:

  var context = new Context(CultureInfo.InvariantCulture);
  context.WithDisabledTags(new [] { "include" }, () =>
  {
  Assert.AreEqual("include usage is not allowed in this context", Template.Parse("{% include 'foo' %}").Render(RenderParameters.FromContext(context, context.FormatProvider)))
  });

[microalps]

1. Looks like there are several previous tasks that are dependencies before this can be merged. Can you describe them and let's chat on gitter about how to get them included?
2. Please make sure all ruby liquid tests are included in new features. e.g. https://github.com/Shopify/liquid/blob/master/test/integration/tags/render_tag_test.rb