Support for named markdown images

[SamyPesse]

See GitbookIO/gitbook#1447

[simov]

I don't know if that could be of any help, but the marked parser already supports that.

[SamyPesse]

Fixed by #16

[simov]

Excuse me but named markdown images refers to [![image-url]][image-link] so the problem is that your parser does not support named image-link with image-url. I'm copy/pasting my other issue here:

---

Things like:

[![travis-ci]][travis]

  [travis-ci]: https://img.shields.io/travis/simov/purest/master.svg?style=flat-square (Build Status - Travis CI)
  [travis]: https://travis-ci.org/simov/purest

As you can see this is rendered correctly in GitHub, the image above have a title and it can be clicked. This doesn't seem to work with latest GitBook:

CLI version: 2.3.0
GitBook version: 3.2.0

---

The PR you are referring to adds support for titles, but not support for named image-link. So I suggest you re-open this issue.

[SamyPesse]

Sorry!