[nerdcubed] Add new extractor

nerdcubed.co.uk describes videos in a single a feed.json file, providing
references to and metadata on >1300 YouTube videos spread across 3 main
channels as well as guest appareances on other channels via a single HTTP
request.

NerdCubedFeedIE transforms this feed into a youtube-dl playlist, preserving
information present in the upstream JSON (allowing zero-cost title/date
matches) and ultimately referencing the embedded YouTube videos.

youtube_dl/extractor/nerdcubed.py

@@ -0,0 +1,36 @@
+# coding: utf-8
+from __future__ import unicode_literals
+
+import datetime
+
+from .common import InfoExtractor
+
+
+class NerdCubedFeedIE(InfoExtractor):
+    _VALID_URL = r'https?://(?:www\.)?nerdcubed\.co\.uk/feed\.json'
+    _TEST = {
+        'url': 'http://www.nerdcubed.co.uk/feed.json',
+        'info_dict': {
+            'title': 'nerdcubed.co.uk feed',
+        },
+        'playlist_mincount': 1300,
+    }
+
+    def _real_extract(self, url):
+        feed = self._download_json(url, url, "Downloading NerdCubed JSON feed")
+        
+        entries = [{
+            '_type': 'url',
+            'title': feed_entry['title'],
+            'uploader': feed_entry['source']['name'] if feed_entry['source'] else None,
+            'upload_date': datetime.datetime.strptime(feed_entry['date'], '%Y-%m-%d').strftime('%Y%m%d'),
+            'url': "http://www.youtube.com/watch?v=" + feed_entry['youtube_id'],
+        } for feed_entry in feed]
+
+        return {
+            '_type': 'playlist',
+            'title': 'nerdcubed.co.uk feed',
+            'id': 'nerdcubed-feed',
+            'entries': entries,
+        }
+