v1.5.0

• Add Greenkeeper support.
• Set minimum node version to >=10.
• Remove custom XO configuration, use defaults.
• Update dependencies:
  • Update to ava@2.1.0
  • Update to coveralls@3.0.4
  • Update to flow-bin@0.100.0
  • Update to nyc@14.1.1
  • Update to xo@0.24.0