Update dependencies.

Author: gkellogg

rdf-spec.gemspec

@@ -22,7 +22,7 @@ Gem::Specification.new do |gem|
   gem.requirements               = []
   gem.add_runtime_dependency     'rdf',             '~> 3.1'
   gem.add_runtime_dependency     'awesome_print',   '~> 1.8'
-  gem.add_runtime_dependency     'rdf-isomorphic',  '~> 3.0'
+  gem.add_runtime_dependency     'rdf-isomorphic',  '~> 3.1'
   gem.add_runtime_dependency     'rspec',           '~> 3.9'
   gem.add_runtime_dependency     'rspec-its',       '~> 1.3'
   gem.add_runtime_dependency     'webmock',         '~> 3.7'