Merge pull request #160 from petervandenabeele/develop

Add a hint about resolving FormatError
Add :unique_bnodes option to writer to ensure that BNodes are uniquely serialized, in spite of any identifier used when they are initialized.
Initialize vocabulary terms with the vocabulary it comes from; add Vocabulary::Term#vocab to retrieve this.
Term accessors must map array members.
Fix some special cases for RDF as a vocabulary.
Remove Data-Vocabulary vocab (RDF::V).
Vocabulary.property/term returns the defined property.
Version 1.1.4.
Finish 1.1.4.

* Update Reader.open documentation to indicate that using the return value as a reader is not well supported, and implementations should restrict themselves to working within a block
* Implement Node#intern using cache, so that Node(\"b\").eql(Node(\"b\")).
  This also allows Statement(:s, p, :o) to eql? Statement(:s, p, :o), where previously the nodes would not be the same.
* Added missing Enumerable#enum_for; it was previously just in Countable and Queryable.
* Major changes to Vocabulary:
  * Refactor Vocabulary using class instance variables.
  * Change RDF vocabulary to delegate to RDF::RDFV, allowing definitions for RDF properties, classes, datatypes along with comments and labels.
  * Implement Vocabulary::Term as subclass of URI used for vocabulary terms. This now implements Vocabulary::Term#label and Vocbulary::Term#comment in addition to Vocabulary.label_for and Vocabulary.comment_for.
  * Implement Vocabulary.to_graph to generate RDF statements for a ruby Vocabulary definition.
  * Change Vocabulary#to_graph to Vocabulary#to_enum (and #enum_for), basically doing the same thing, but avoiding emergent problems.
  * Rename HTTP vocabulary to HT, to avoid unfortunate prefix, and to be consistent with general use.
  * Describe fuller vocabulary DSL.
  * Implement Vocabulary.expand_pname.
  * Update vocabulary generation to serialize all properties (with no language or language \"en\")
  * Update all built-in vocabularies.
  * Use our own version of xsd RDFS vocabulary. Update RDF vocabulary.
  * Implement respond_to? and method_missing for Vocabulary::Term to create attribute accessors.
  * Move vocabulary loading from CLI method to Vocabulary.load; use for generating vocabularies.
  * Add RDF::Vocabuarly.find and .find_term to lookup URIs.
  * Remove Data-Vocabulary vocab (RDF::V).
  * Initialize vocabulary terms with the vocabulary it comes from; add Vocabulary::Term#vocab to retrieve this.
* Implement URI#pname to create a string form of URI#qname.
* Add :unique_bnodes option to writer to ensure that BNodes are uniquely serialized, in spite of any identifier used when they are initialized.
Finish rspec3.0
Don't verify SSL connections.
Added Vocabulary.imports to return the owl:imports definition as defined in the original vocabulary.
Allow imports to return an empty array, even if vocabulary has no imports statement.
Memoize imports.
Added Vocabulary.imported_from to return all vocabularies that import self.
Added __imports__ as an alias for imports.
Regenerate vocabularies.
Fix problem in vocabulary loading and generation and regenerate vocabularies.
Add back rdf.data-vocabulary.org and add data-vocabulary (VMD) as a cleaned-up version used in practice.
Fix bug in Vocabulary.[] where enumerable type methods would be called instead of a vocabulary term being defined.
Base VMD vocabulary on V (data-vocab), using equivalent definitions in different namespaces.
More updates for data-vocabulary to bring in line with examples.