Release 1.1.5

* schema.org version 1.9
* Add Vocabulary::Term#each_statement, #enum_for, and #to_enum.
* Fully implement Vocabulary::Term#domain_includes/#range_includes
* From Queryable#query, make sure that #query_execute is called with a block, as that's the published interface
* Simplify encoding handling of ntriples unescape (@ewout)
* Add deprecation warnings for use of Surrogate Pairs and other areas previously commented as being deprecated:
  * URI subject to list (other than rdf:nil)
  * Writer#write_graph
  * Writer#write_statements
Back-off on deprecation IRIs as list subjects, as it's common to prospectively create a list to see if it's valid.
Version 1.1.5.1.
Finish 1.1.5.1

* Back-off on deprecation IRIs as list subjects, as it's common to prospectively create a list to see if it's valid.