v1.0.0-rc.3

Continued thanks to the community for their help in reporting and fixing issues in for Relay Modern! We hope you'll keep trying out the release candidates and continue to report how its going.

Changes since rc.2:

• Fixed most common issue with using RelayModern directly (#1665)
• New API: Environment.check() (1c585b2)
• Improved generated Flow types
• Internal API: Renamed "RelayStatic" to "RelayModern" in a number of places
• Fixed last warning from using React.PropTypes
• Improvements to relay-compiler including ignoring node_modules and supporting custom file extensions.