create and use RDF vocab for Triannon:externalReference
Merge pull request #60 from sul-dlss/triannon-rdf-vocab

create and use RDF vocab for Triannon:externalReference
add turtle versions of 3 annotation fixtures
add comment to Triannon::LdpToOaMapper.ldp_to_oa method
fixing failing spec
add 2 vcr cassettes for LdpCreator.create_body_resources specs
partial implementation of LdpCreator.create_body_resources
fix 2 failing specs for LdpCreator.bodies_graph
add fixture for the bodies of the body-choice graph as has uris
convert LdpCreator specs to do graph queries instead of string matches on results