Update the Semaphore badge to the shield badge type

**Why is this needed?**
It just does look better in the Readme :-)
Signed-off-by: Jeroen van Baarsen <jeroenvanbaarsen@gmail.com>

README.md

 # GitLab
 
 [![build status](https://ci.gitlab.com/projects/1/status.png?ref=master)](https://ci.gitlab.com/projects/1?ref=master)
-[![Build Status](https://semaphoreapp.com/api/v1/projects/2f1a5809-418b-4cc2-a1f4-819607579fe7/243338/badge.png)](https://semaphoreapp.com/gitlabhq/gitlabhq)
+[![Build Status](https://semaphoreci.com/api/v1/projects/2f1a5809-418b-4cc2-a1f4-819607579fe7/400484/shields_badge.svg)](https://semaphoreci.com/gitlabhq/gitlabhq)
 [![Code Climate](https://codeclimate.com/github/gitlabhq/gitlabhq.svg)](https://codeclimate.com/github/gitlabhq/gitlabhq)
 [![Coverage Status](https://coveralls.io/repos/gitlabhq/gitlabhq/badge.png?branch=master)](https://coveralls.io/r/gitlabhq/gitlabhq?branch=master)