Smarter inference, better output

• Highlight all Markdown, not just examples. Fixes #610
• Fix for --config only strip comments on json files (#611)
• Merge inferred return type like we do for params. Refs #359 (#604)
• Support webpack's System.import with nice handy babel plugin (#603)
• Format optional types with ? instead of [] (#538)
• Fix membership assignment for old-fashioned prototype members (#599)
• Update Node API documentation to include only exposed API surface (#585)
• Add too-much-inference troubleshooting topic