Fix #218 and https://forum.cozy.io/t/gitlab-for-installing-apps/159/5

* Fix #218 
* Fix https://forum.cozy.io/t/gitlab-for-installing-apps/159/5 : authorized gitlab url with http. @frankrousseau, are you ok with that ?
You could use [url](http://nodejs.org/api/url.html) node module to retrieve more properly the protocol.