Added createGist operation and amended authorization lookup

Added createGist operation and amended authoization lookup not to just
take position 0. Instead changed lookup to iterate authorizations and
check for one with a matching scope.
Fix to scope check

Changed to scope check to containsAll to make sure authorization
contains every requested scope.
Tidy up.

Tidy up formatting.
Tidy up

Tidy up formatting.
Updated doc xml sample

Updated doc xml sample for createGist