message: add build status logo
diff: # HermitCore - A lightweight unikernel for a scalable and predictable runtime behavior
  +[![Build Status](https://travis-ci.org/RWTH-OS/HermitCore.svg?branch=master)](https://travis-ci.org/RWTH-OS/HermitCore)
  +
  The project [HermitCore]( http://www.hermitcore.org ) is a new
  [unikernel](http://unikernel.org) targeting a scalable and predictable runtime
  for high-performance and cloud computing. HermitCore extends the multi-kernel
  