Relax dependencies to allow for 3.0 release.

Author: gkellogg

rdf-mongo.gemspec

@@ -29,10 +29,10 @@ Gem::Specification.new do |gem|
 
   gem.required_ruby_version      = '>= 2.2.2'
   gem.requirements               = []
-  gem.add_runtime_dependency     'rdf',             '~> 2.0'
+  gem.add_runtime_dependency     'rdf',             '>= 2.2', '< 4.0'
   gem.add_runtime_dependency     'mongo',           '~> 2.2'
 
-  gem.add_development_dependency 'rdf-spec',        '~> 2.0'
+  gem.add_development_dependency 'rdf-spec',        '>= 2.2', '< 4.0'
   gem.add_development_dependency 'rspec',           '~> 3.4'
   gem.add_development_dependency 'rspec-its',       '~> 1.2'
   gem.add_development_dependency 'yard',            '~> 0.8'