Add CreatedAtTime() convenience wrapper function
Add GetOEmbedId (fetch an OEmbed by specifying the tweet Id)
 Implement GetFriendsIdsAll (which returns a channel)

*  GetFriendsIdsAll pre-fetches in the background
Run gofmt
Fix bug where errors that are not rate-limiting errors are swallowed
Add media entity type.

Please see the api reference here:
https://dev.twitter.com/docs/entities
.. under "media"

Signed-off-by: aditya <dev@chimeracoder.net>
Run gofmt on previous patch from @nabkey
Fix MediaSize/MediaSizes definition, and add (passing) test for entities