added rspec dependency

Author: klobuczek

jsonapi_spec_helpers.gemspec

@@ -23,5 +23,5 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "actionpack", "~> 5.0"
   spec.add_development_dependency "bundler", "~> 1.11"
   spec.add_development_dependency "rake", "~> 10.0"
-  spec.add_development_dependency "rspec", "~> 3.0"
+  spec.add_dependency "rspec", "~> 3.0"
 end

lib/jsonapi_spec_helpers/matchers.rb

@@ -1,3 +1,5 @@
+require 'rspec/matchers'
+
 RSpec::Matchers.define :match_payload do |attribute, expected|
   match do |actual|
     if expected.respond_to?(:as_json)