Simplify and test relationship_segments

Author: lgebhardt

lib/jsonapi/path.rb

@@ -25,11 +25,7 @@ def initialize(resource_klass:,
     end
 
     def relationship_segments
-      relationships = []
-      @segments.each do |segment|
-        relationships << segment if segment.is_a?(PathSegment::Relationship)
-      end
-      relationships
+      @segments.select {|p| p.is_a?(PathSegment::Relationship)}
     end
 
     def relationship_path_string

test/unit/paths/path_test.rb

@@ -40,6 +40,8 @@ def test_two_relationships_and_field
     assert_equal Api::V1::PostResource._relationship(:comments), path.segments[0].relationship
     assert_equal Api::V1::CommentResource._relationship(:author), path.segments[1].relationship
     assert_equal 'name', path.segments[2].field_name
+
+    assert_equal 2, path.relationship_segments.length
   end
 
   def test_two_relationships_and_parse_fields_false_raises_with_field