Default to empty graph if no graph supplied to initializer
Merge pull request #338 from projecthydra/default_empty_graph

Default to empty graph if no graph supplied to initializer
Datastream#prefix should only be applied to fields defined by that datastream. Fixes #340
abstract nokogiri-related DS methods into a reusable mixin
Merge pull request #341 from projecthydra/prefixes_only_ds_properties

Datastream#prefix should be applied to fields defined by that datastream
Merge pull request #342 from barmintor/nokogiri_mixin

abstract nokogiri-related DS methods into a reusable mixin
Move #where and #order into QueryMethods and test for immutability
Merge pull request #344 from projecthydra/chained-where-relations

Move #where and #order into QueryMethods and test for immutability
there's really no difference between Datastreams.has_metadata and Datastreams.has_file_datastream
Merge pull request #345 from barmintor/datastream_helpers

remove copycode in DS model helpers
Refactor attribute methods for simplicity and readability
Merge pull request #348 from projecthydra/simplify_attributes

Refactor attribute methods for simplicity and readability
Remove validate_content_present
Frozen datastreams should be able to load content from fedora but not mutate the content
Change the erasure of datastream_object_for to accept a hash of options, like the method in rubydora does.
Merge pull request #350 from projecthydra/rubydora_1.7.1

Rubydora 1.7.1
Bump to 7.0.0.rc2
slightly better graph manangement on rdf lists
Merge branch 'master' into rdf
Rdf_Datastream#content= probably shouldn't set #new? to false, if the resource is unpersisted. It probably also shouldn't persist. (is this test really necessary?)