readme toc subcommand fails to run in docker container

https://github.com/coala/coala-vs-code

```
docker run --rm -v $(pwd):/workdir gaocegege/maintainer readme toc

Table of Contents
=================

2017/05/01 15:48:27 There is no config file defined.
awk: cmd. line:2: %*x formats are not supported


Created by [gh-md-toc](https://github.com/ekalinin/github-markdown-toc)
2017/05/01 15:48:29 TOC generated successfully.
```