This is a Ruby on Rails poker app that I work on from time to time. It's just something I'm doing for kicks, so there won't be much documentation or indeed much functionality. Good luck!
Things you may want to cover:
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Ruby version
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System dependencies
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Configuration
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Database creation
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Database initialization
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How to run the test suite
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Services (job queues, cache servers, search engines, etc.)
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Deployment instructions
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...