Several errors occur.

[kevinbird61]

• [x] Merging process has some wrong behavior.
• [ ] Markdown transformer aren't robust enough
• [ ] Consider markdown transformer lib: markdown-to-ast will have difference behavior when input source is complicated. Need to fix it.

[kevinbird61]

Prepare to rebuild docogen-md-engine.js

• Make sure the data structure in markdown-to-ast.