Revisit parser architecture

[zdne]

Revisit parser architecture.

Improve the parser architecture so it is easier to introduce new syntax (particularly list-based section) and maintain the older one.

This includes:

• Separate Markdown parser from Snow Crash
• Use Markdown AST (tree) instead of a flat stack of blocks
• Provide uniform interface for processing markdown sections regardless of the definition type (markdown header or list)
• Revisit work with source maps (range conversations)
• Simplify unit tests – No need to construct Markdown AST in tests – parse Markdown / Blueprint directly

[zdne]

New Parser Architecture Proof of Concept

https://gist.github.com/zdne/55b7a38f52ca642e123b

Markdown Parser

https://github.com/apiaryio/markdown-parser

[zdne]

Progress-tracking Wiki page: https://github.com/apiaryio/snowcrash/wiki/Refactor-Progress