message: Add circle-ci badge
diff: <img src="https://travis-ci.org/lief-project/LIEF.svg?branch=master">
  </a>
  &nbsp;
  + <a href="https://circleci.com/gh/lief-project/LIEF/tree/master">
  + <img src="https://circleci.com/gh/lief-project/LIEF/tree/master.svg?style=svg">
  + </a>
  + &nbsp;
  <a href="https://ci.appveyor.com/project/Romain/lief/branch/master">
  <img src="https://ci.appveyor.com/api/projects/status/0ijlcujac5vh8cas/branch/master?svg=true">
  </a>
  <a href="https://github.com/lief-project/LIEF/releases">
  <img src="https://img.shields.io/badge/release-0.7.0-brightgreen.svg?style=default">
  </a>
  -
  </p>
  The purpose of this project is to provide a cross platform library which can parse, modify and abstract ELF, PE and MachO formats.
  