Anchor links are not working without explicit path specification

[slavafomin]

Hello!

Thank you for this great library!

However, it looks like anchor links are not working without explicit path specification.

For example, I have this code in my index.md:

# Introduction

Also see [pagination](#pagination).

# Pagination

Most of the requests which return list of items support pagination.

When I try to compile it, I'm getting the error:

Could not parse metadata from /src/index.md
path.js:7
    throw new TypeError('Path must be a string. Received ' + inspect(path));
    ^

TypeError: Path must be a string. Received null
    at assertPath (path.js:7:11)
    at Object.extname (path.js:1433:5)
    at Renderer.renderer.link (.../node_modules/markdown-styles/lib/convert-md.js:58:22)
    at InlineLexer.outputLink (.../node_modules/markdown-styles/node_modules/marked/lib/marked.js:707:21)
    at InlineLexer.output (.../node_modules/markdown-styles/node_modules/marked/lib/marked.js:622:19)
    at Parser.tok (.../node_modules/markdown-styles/node_modules/marked/lib/marked.js:1075:50)
    at Parser.parse (.../node_modules/markdown-styles/node_modules/marked/lib/marked.js:935:17)
    at DestroyableTransform._transform (.../node_modules/markdown-styles/node_modules/markdown-stream-utils/lib/convert-md.js:11:28)
    at DestroyableTransform.Transform._read (.../node_modules/markdown-styles/node_modules/readable-stream/lib/_stream_transform.js:184:10)
    at DestroyableTransform.Transform._write (.../node_modules/markdown-styles/node_modules/readable-stream/lib/_stream_transform.js:172:12)

However, when I specify it like this: Also see [pagination](./#pagination)., it compiles correctly but leads out of index.html file to the root of the directory. The only working solution is to write it this way: Also see [pagination](./index.html#pagination)., but it's cumbersome and not very DRY.