Electron Render Service Versions Save

• Delayed rendering support by @ekristen
• Update Electron to v0.37.8
• Validate endpoints input with express-validator
• More cachable Dockerfile
• Basic integration test suite with Travis

Breaking API changes:

• Rename access_key to accessKey
• Rename INTERFACE env variable to HOSTNAME
• Image clipping rectangle variables are nested under clippingRect

• Use Debian Jessie for Docker image base
• Run electron directly in image instead of npm start

• Fix subresource loading bug
• Add removePrintMedia flag to PDF rendering
• Document Docker shared memory

• Split code up
• Add support for PNG/JPEG output
• Add more error handling