Document GitLab CI integration

Author: dfyx

docs/build-server-support/build-server-support.md

@@ -4,6 +4,7 @@ GitVersion has support for quite a few build servers out of the box. Currently w
  - [AppVeyor](build-server/appveyor.md)
  - [Bamboo](build-server/bamboo.md)
  - [Continua CI](build-server/continua.md)
+ - [GitLab CI](build-server/gitlab.md)
  - [Jenkins](build-server/jenkins.md)
  - [MyGet](build-server/myget.md)
  - [Octopus Deploy](build-server/octopus-deploy.md)
@@ -14,4 +15,4 @@ GitVersion has support for quite a few build servers out of the box. Currently w
 When GitVersion.exe is run with the `/output buildserver` flag instead of outputting Json it will export variables to the current build server.
 For instance if you are running in TeamCity after you run `GitVersion /output buildserver` you will have the `%system.GitVersion.SemVer%` available for you to use
 
-When running in MSBuild either from the [MSBuild Task](/usage/msbuild-task) or by using the `/proj myproject.sln` parameter, GitVersion will make the MSBuild variables available in the format `$(GitVersion_SemVer)`.
+When running in MSBuild either from the [MSBuild Task](/usage/msbuild-task) or by using the `/proj myproject.sln` parameter, GitVersion will make the MSBuild variables available in the format `$(GitVersion_SemVer)`.

docs/build-server-support/build-server/gitlab.md

@@ -0,0 +1,3 @@
+# GitLab CI
+
+To use GitVersion with GitLab CI, either use the [MSBuild Task](/usage/msbuild-task) or put the GitVersion executable in your runner's `PATH`.