PULL_REQUEST_TEMPLATE.md

Before submitting your PR, please review the following checklist:

• I have signed the RethinkDB CLA.
• CONSIDER adding a unit test if your PR resolves an issue.
• DO keep pull requests small so they can be easily reviewed.
• DO make sure unit tests pass.
• DO make sure any public APIs are XML documented.
• DO make sure not to introduce any compiler warnings.
• AVOID breaking the continuous integration build.
• AVOID making significant changes to the driver's overall architecture.