Add Youtube embeds

This will embed a youtube video inline on the page. Hopefully it works!

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

tests/test_replybuilder.py

@@ -103,3 +103,15 @@ what happened to the 1 2 3 4 5 6 7 8 9
         for input, output in expected:
             rb = ReplyBuilder(input.strip(), parse_spoilers=True)
             self.assertEquals(rb.build(), output)
+
+    def test_youtube_embed(self):
+        expected = [
+            (
+                "https://www.youtube.com/watch?v=O_3_-UrhZH0",
+                '<span class="youtube_embed"><span class="youtube_embed_container">https://www.youtube.com/watch?v=O_3_-UrhZH0 [<a class="youtube_embed_link" data-yt-hash="O_3_-UrhZH0" href="https://www.youtube.com/watch?v=O_3_-UrhZH0">Embed</a>]</span></span>',
+            ),
+        ]
+
+        for input, output in expected:
+            rb = ReplyBuilder(input.strip())
+            self.assertEquals(rb.build(), output)