Integrate YouTube videos for events

Concept:

1. Videos are recorded professionally and uploaded to YouTube: 
    http://www.youtube.com/channel/UCGQZd1FaRdbZGnOuzh_n9Zg/videos
2. Each event listing will display the videos which have the date recorded set to the date of the event.

Challenges:

1. YouTube does not support the V2 API for Google+ accounts like DCPython
2. YouTube's v3 API to search for videos belonging to a specific user or channel either return errors or no results for DCPython or require user authentication

Approach:

1. Use the videos@dcpython.org account to issue access keys
2. Create a playlist per meetup containing the event date in the title
3. When we want to display videos from a meetup, we search for any playlist which has either an exact match on the event name or which contains the event date in ISO 8601 format (i.e. YYYY-MM-DD) in the title.

Todo:
* ~~Retrieving playlists and videos from YouTube~~
* ~~Add playlist template tag~~
* Move playlist embed to event detail page when we add it to avoid rendering many embedded players on the event list