Render API Blueprint as Markdown

[API Blueprint](https://github.com/apiaryio/api-blueprint) is a Markdown based description language for Web APIs. 

Ideally an API description – an API blueprint – lives in the repository with the API implementation, readable by API users and integrated with a CI which tests any changes to API implementation or the blueprint itself.

An example of an API Blueprint can be found [here](https://github.com/zdne/gistfox-api/blob/master/apiary.apib). Some real-world examples are [here (Tesla Model S API)](https://github.com/timdorr/model-s-api/blob/master/apiary.apib) or [here (PODServe API)](https://github.com/dwcaraway/podserve/blob/master/apiary.apib).

Not sure whether this PR should be to `master` or `release-1.0.1`. Let me know, should something need to be changed.