Update dependencies.

Author: gkellogg

rdf.gemspec

@@ -38,9 +38,9 @@ Gem::Specification.new do |gem|
   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',       '~> 3.13'
   gem.add_development_dependency 'rspec-its',   '~> 1.3'
-  gem.add_development_dependency 'webmock',     '~> 3.19'
+  gem.add_development_dependency 'webmock',     '~> 3.23'
   gem.add_development_dependency 'yard',        '~> 0.9'
   gem.add_development_dependency 'faraday',     '~> 1.10'
   gem.add_development_dependency 'faraday_middleware', '~> 1.2'