open to work attribute youtube_user_name
add youtube_user_name to class SubscriptionFeedParser

This feature need for future identificate owner of user subscription. If we render field title, then can get a user name in  "display" wich can not operate with standart queries.
adding content_length option for remote videos
Fixing embed_html5 tab alignment
Allow the sandbox attribute to be set on the html5 embed
Loosening json dependency
loosen the nokogiri dependency
Add User#channel_uri.
Refactor errors.

- Add some tests to assure error raising from client is correct
- Define the current errors under the YouTubeIt namespace
Introduce ResourceNotFoundError.

- Is raised whenever the api responds with 404
- Used to raise UploadError which made no sense at all for a missing video etc
Add changelog with info about changes to error handling.
adding retrieve region and category-specific standard video feeds
Fix syntax error in sample code.
fixes media content format parsing
adds attr_readers to the video format
Add channel_id to Comment
Update test
Add googlePlusUserId to Comment
loosen the nokogiri dependency
Adding fullscreen option for HTML5 embed

Without this option the full screen youtube option doesn't work