Make #have_relationships accept symbols

Author: lancedikson

Diff for: lib/jsonapi/rspec/relationships.rb

@@ -26,7 +26,7 @@ module Relationships
         match do |actual|
           return false unless actual.key?('relationships')
 
-          rels.all? { |rel| actual['relationships'].key?(rel) }
+          rels.all? { |rel| actual['relationships'].key?(rel.to_s) }
         end
       end
     end