Release 1.1.4.1.

* Don't reference count statement subjects, only objects. This helps determine propery embedding.
* Make sure that Writer#get_curie always returns a string.
Update REXML support to ensure it is free of native dependencies (nokogiri, equivalent-xml, microdata).
Update travis build matrix to use Gemfile-pure.
Update expansion vocabularies (foaf, schema).
Use http://schema.org/docs/schema_org_rdfa.html for schema.org, instead of schema.rdfs.org.
Manually add additionalType rule for schema.org expansion.
First pass at using rdf-reasoner, instead of built-in entailment rules to do graph expansion.
[CI skip]
Use rdf-reasoner for vocabulary expansion. This generates many more triples, so test using SPARQL rather than graph isomorphism.

* Works with built-in vocabularies, doesn't load vocabularies at this point.
Dynamically load vocabularies.
Use RDF.rb vocabularies, but built-in entailment rules, rather than reasoner.
Version 1.1.5.
Release 1.1.5

* Use RDF.rb vocabularies, but built-in entailment rules, rather than reasoner.
* Dynamically load vocabularies.