Release 2.0.0

Updates for RDF.rb 2.0

• Specs for Queryable#query tested internal implementation rather than behavior, this caused issues for classes mixing in Queryable, but delegating #query to some collaborator. See, e.g. ActiveTriples/ActiveTriples#169. This tests the contract directly, instead.
• Add tests for Transaction, Changeset, and Dataset
• Refactor Queryable specs
  • #33 created some duplicate tests; this refactors by moving them into a shared example set.
  • Additionally, it skips specs for #query_pattern and #query_execute if they are not defined by the Queryable. This allows implementations to fulfill the #query interface directly, if desired.
• Disable an enumerable test unless the subject supports named graphs. (Moved some other checks inside the spec, where it's defined).
• In Mutable, when doing deletes with patterns, make sure to not use BNodes, which might not be supported by repository implementation.
• Add RDF::Spec.logger, which creates a Logger instance using a StringIO. Also implements #clear and #to_s instance methods.
• Added be_equivalent_graph and produce matchers.
• Simplify Enumerable#has_statement? spec as both Repositories and Graphs should have a statement, either matching on graph_name, or ignoring it. Previously, if a Graph had a bound graph_name it would need to match that in the statement, but this is inconsistent with the notion that a graph has only triples.
• Change Queryable#first_* specs to not depend on query result ordering.
• Add a round-trip check for Writers also having a Reader to ensure that different BNodes having the same identifier get written out with unique identifiers (see ruby-rdf/rdf/issues/262).
• Soften RDF::Transaction buffering requirements
• Not every Transaction needs to keep an up-to-date Changeset in buffer. This change loosens the requirements. some of the tests are removed to the rdf test suite in spec/transaction_spec.rb.
• Introduce RDF::Dataset as a distinct concept
  • Dataset is introduced as a base class of RDF::Repository. It represents a (default read only) set of graphs. Some of the specs are removed from the repository specs, but are re-included indirectly through dataset's tests.
• Test atomic/transactional #delete_insert application
  • When a Mutable #supports?(:transactions), #delete_insert is guaranteed to update atomically.
  • Repository#delete_insert always applies within a transaction scope and conforms to the individual Repository`s transaction semantics.
• Check durability by re-creating the repository using uri and verifying that when subject is updated, the new instance is also updated. Fixes #52.
• Skip mutable and writable tests unless resource is mutable or writable. This is better than testing separately in each test.
• Avoid changing Repository while tx is in progress
  • Adding or deleting statements in the Repository causes serializable transactions to break (correctly). Instead, prepare the repository state before beginning the test transaction.
• Test isolation semantics for transactions.
• Fix array inspector when values are hashes.
• Allow formats to not have readers (vocabulary is a write-only format).