91 allow includes strings (Netflix#93)

* add hash benchmarking to performance tests

* Add missing attribute in README example

* Disable GC before doing performance test

* Enable oj to AM for fair benchmark test

* add information on performance methodology

* add oss metadata

* Make an error that demonstrates [Issue

* Simple RSpec test that fails with a non-empty string but passes with a
non-empty symbol
* To run the test, rspec spec/lib/object_serializer_spec.rb

* Map includes to symbols if they are provided as strings

* Includes would fail with an ArgumentError unless they were explicitly
provided as symbols (see Netflix#97)
* This is solved by mapping the strings to symbols in the
ObjectSerializer initializer
* No real impact on performance here

Author: sjmog

lib/fast_jsonapi/object_serializer.rb

@@ -84,7 +84,7 @@ def process_options(options)
       @meta = options[:meta]
 
       if options[:include].present?
-        @includes = options[:include].delete_if(&:blank?)
+        @includes = options[:include].delete_if(&:blank?).map(&:to_sym)
         validate_includes!(@includes)
       end
     end

spec/lib/object_serializer_performance_spec.rb

@@ -33,6 +33,9 @@
     }
   }
 
+  before(:all) { GC.disable }
+  after(:all) { GC.enable }
+
   context 'when testing performance of serialization' do
     it 'should create a hash of 1000 records in less than 50 ms' do
       movies = 1000.times.map { |_i| movie }

spec/lib/object_serializer_spec.rb

@@ -89,6 +89,12 @@
       expect { MovieSerializer.new([movie, movie], options).serializable_hash }.to raise_error(ArgumentError)
     end
 
+    it 'does not throw an error with non-empty string array includes key' do
+      options = {}
+      options[:include] = ['actors']
+      expect { MovieSerializer.new(movie, options) }.not_to raise_error
+    end
+
     it 'returns keys when serializing with empty string/nil array includes key' do
       options = {}
       options[:meta] = { total: 2 }