v1.1.0

• Set minimum node version to >=6.
• Add code coverage report using coveralls and nyc.
• Update dependencies:
  • Update to ansi-escapes@3.1.0
  • Update to chalk@2.4.1
  • Update to log-symbols@2.2.0
  • Update to plur@3.0.1
  • Update to string-width@2.1.1
  • Update to ava@0.25.0
  • Update to strip-ansi@4.0.0
  • Update to xo@0.21.1
• Cleanup some files.