Embedding external images in README.md (BB-6489)

If I embedd an image in my README.md (for example my TeamCity build status icon) the image is not rendered, only a placeholder appears.

The code used in the README.md:

#!markdown
![Build Status](https://teamcity.wegtam.com/TeamCity/app/rest/builds/buildType:%28id:bt5%29/statusIcon)

Maybe it is of interest that the README.md is located in a private repository.