auto add CI shields

[wilzbach]

The workmen should automatically check whether there is a travis server running and add the corresponding shields.

Possible ways:

1. Query directly for the img

https://api.travis-ci.org/greenify/biojs-vis-msa.svg?branch=master

on error it will return

{"file":"not found"}

1. Use the travis-ci API client (better)

Probably the repo command is useful

https://api.travis-ci.org/repos/greenify.json
https://api.travis-ci.org/repos/greenify/biojs-vis-msa.json

(they both return {"file":"not found"} on an error).