Updates for RDF 1.1.
Remove 1.8.x support and preliminary update for VERSION.
Update dependencies for RDF 1.1. Use json gem instead of json_pure, as json is built into all rubies now.
Update to RSpec expect syntax and use webmock for remote resources.
Update travis to run unrestricted version of JRuby
Add rdf-aggregate-repo to Gemfile.
Revert use of Enumerator for solutions.
Update Travis test matrix to use rbx instead of rbx-mode19
Finish 1.1.0
Use Nokogiri instead of REXML for parsing results.

Nokogiri is significantly faster, and now has a pure-java backend for
use on JRuby.

This patch potentially breaks backwards compatibility, as
parse_xml_bindings no longer accepts REXML elements.
Add Nokogiri dep to README.
Add Nokogiri as development dependency.
Add test for XML results parsing.

This doesn't really fit into rspec very well, but it works.