Implements more embed codes for events
- add slideshare embed code

TODO:
- review help texts
- refactor video_type  collection to event model enumeration
- add more embed code (flickr, instagram, myvideo)
- video_type and video_id is now more like media_type and media_id -> it should considered to rename these attributes
#26
Implements more embed codes for events
- refactor video_type  collection to event model enumeration
#26
Implements flickr embedded for events
#26