update to blackfriday v2.0.0 API

[tamird]

https://github.com/russross/blackfriday/releases/tag/v2.0.0

[zevdg]

As a temporary measure, the import could at least be changed to gopkg.in/russross/blackfriday.v1

That or if this project were updated to use dep, a version constraint could be put on blackfriday

[[constraint]]
  name = "github.com/russross/blackfriday"
  version = "1.4"

FYI, this causes issues for anyone who tries to import this package using dep.

[cpuguy83]

@zevdg It's already vendored.

[tamird]

Some tools flatten dependencies' vendor directories, fwiw.

[cpuguy83]

Happy to use dep if someone wants to convert it over.
Also if gopkg is the canonical import path, happy to use that as well.

[cpuguy83]

Being implemented in #33