Update dependencies.

Author: gkellogg

rdf.gemspec

@@ -31,10 +31,10 @@ Gem::Specification.new do |gem|
   gem.requirements               = []
   gem.add_runtime_dependency     'link_header', '~> 0.0', '>= 0.0.8'
   gem.add_runtime_dependency     'bcp47_spec',  '~> 0.2'
-  gem.add_development_dependency 'rdf-spec',    '~> 3.2'
-  gem.add_development_dependency 'rdf-turtle',  '~> 3.2'
-  gem.add_development_dependency 'rdf-vocab',   '~> 3.2'
-  gem.add_development_dependency 'rdf-xsd',     '~> 3.2', '>= 3.2.1'
+  gem.add_development_dependency 'rdf-spec',    '~> 3.3'
+  gem.add_development_dependency 'rdf-turtle',  '~> 3.3'
+  gem.add_development_dependency 'rdf-vocab',   '~> 3.3'
+  gem.add_development_dependency 'rdf-xsd',     '~> 3.3'
   gem.add_development_dependency 'rest-client', '~> 2.1'
   gem.add_development_dependency 'rspec',       '~> 3.12'
   gem.add_development_dependency 'rspec-its',   '~> 1.3'