highlights return successfully with a GET request

NOTE: This is undocumented and unconfirmed by Instapaper, but was
discovered through trial and error.

lib/instapaper/api/highlights.rb

@@ -7,7 +7,7 @@ module Instapaper
       # List highlights for a bookmark
       # @param bookmark_id [String, Integer]
       def highlights(bookmark_id)
-        perform_post_with_objects("/api/1.1/bookmarks/#{bookmark_id}/highlights", {}, Instapaper::Highlight)
+        perform_get_with_objects("/api/1.1/bookmarks/#{bookmark_id}/highlights", {}, Instapaper::Highlight)
       end
 
       # Create a new highlight

lib/instapaper/http/utils.rb

@@ -12,6 +12,13 @@ module Instapaper
         perform_request_with_objects(:post, path, options, klass)
       end
 
+      # @param path [String]
+      # @param options [Hash]
+      # @param klass [Class]
+      def perform_get_with_objects(path, options, klass)
+        perform_request_with_objects(:get, path, options, klass)
+      end
+
       # @param request_method [Symbol]
       # @param path [String]
       # @param options [Hash]

spec/instapaper/api/highlights_spec.rb

@@ -5,13 +5,13 @@ describe Instapaper::Client::Highlights do
 
   describe '#highlights' do
     before do
-      stub_post('/api/1.1/bookmarks/123/highlights')
+      stub_get('/api/1.1/bookmarks/123/highlights')
         .to_return(status: 200, body: fixture('highlights_list.json'), headers: {content_type: 'application/json; charset=utf-8'})
     end
 
     it 'gets the correct resource' do
       client.highlights(123)
-      expect(a_post('/api/1.1/bookmarks/123/highlights')).to have_been_made
+      expect(a_get('/api/1.1/bookmarks/123/highlights')).to have_been_made
     end
 
     it 'returns an array containing folders on success' do

spec/spec_helper.rb

@@ -13,10 +13,18 @@ def a_post(path)
   a_request(:post, Instapaper::HTTP::Request::BASE_URL + path)
 end
 
+def a_get(path)
+  a_request(:get, Instapaper::HTTP::Request::BASE_URL + path)
+end
+
 def stub_post(path)
   stub_request(:post, Instapaper::HTTP::Request::BASE_URL + path)
 end
 
+def stub_get(path)
+  stub_request(:get, Instapaper::HTTP::Request::BASE_URL + path)
+end
+
 def fixture_path
   File.expand_path('../fixtures', __FILE__)
 end