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.
Set output encoding to UTF-8 in Writer and CLI for JRuby.
Add JRuby back for normal Travis processing!
Improve RDF generation from vocabulary terms for non-distinctive attributes.
Date/Time/DateTime timezone updates:

* Add #has_timezone? (#has_tz?) to Date, Time and DateTime.
* Add #tz to Date, used for recovering timezone from lexical representation.
* Date canonicalization does not normalize to UTC per XSD canonicalization instructions.
More date/time/dateTime tests.
* Represent Literal::Time using ::DateTime instead of ::Time, as ::Time looses any declared timezone.
* Add Time#tz and Date#tz.
Added Literal#humanize defaulting to #to_s. Special implementations for Date, Time, and DateTime.
Update for schema.org 1.91
Version 1.1.6.
Release 1.1.6.

* Set output encoding to UTF-8 in Writer and CLI for JRuby.
* Improve RDF generation from vocabulary terms for non-distinctive attributes.
* Date/Time/DateTime timezone updates:
  * Add #has_timezone? (#has_tz?) to Date, Time and DateTime.
  * Add #tz to Date, used for recovering timezone from lexical representation.
  * Date canonicalization does not normalize to UTC per XSD canonicalization instructions.
* Represent Literal::Time using ::DateTime instead of ::Time, as ::Time looses any declared timezone.
* Add Time#tz and Date#tz.
* Added Literal#humanize defaulting to #to_s. Special implementations for Date, Time, and DateTime.
* Update for schema.org 1.91