* 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 #97)
* This is solved by mapping the strings to symbols in the
ObjectSerializer initializer
* No real impact on performance here
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