allow options, such as :tracking_id to be provided to #create_pack.
make tracking_id a parameter
use 2-legged oauth

this allows us to simplify Moo::Client
ignore metadata
be consistent about key symbolization
tidy up model serialization
add the 'small-preview' image basket item type
add an example
update the README
Merge remote-tracking branch 'eoin/master'
Merge remote-tracking branch 'origin/master'

Conflicts:
	README.mkd