Document all the available YouTube V3 API methods
Use gzip for YouTube API requests

But don't show the gzip headers when printing the "curl"
format of a response, so repeating it shows the uncompressed
response.
Remove unused method
New content-details methods for videos

- Video#stereoscopic?
- Video#hd?
- Video#captioned?
- Video#licensed?
Fix :ignore_errors in delete_all

If delete_all is invoked with :ignore_errors, then any error
occurring in the deletion of any single item should be ignored too.
Better error message for Errors::NoItems

Like every other error, report the failing request in cURL format
when the error occurs.
Merge branch 'miscellaneous-improvements'