Added Unity DLLs path relative to Unity installation directory

Author: neuroKip

docs/contributing/how-to-build.md

@@ -40,11 +40,11 @@ To be able to authenticate in GitHub for Unity, you'll need to:
 - [Register a new developer application](https://github.com/settings/developers) in your profile.
 - Copy [common/ApplicationInfo_Local.cs-example](../../common/ApplicationInfo_Local.cs-example) to `common/ApplicationInfo_Local.cs` and fill out the clientId/clientSecret fields for your application.
 
-The build needs to reference `UnityEngine.dll` and `UnityEditor.dll`. These DLLs are included with Unity. If you've installed Unity in the default location, the build will be able to find them automatically. If not, copy these DLLs from your Unity installation into the `lib` directory in order for the build to work.
+The build needs to reference `UnityEngine.dll` and `UnityEditor.dll`. These DLLs are included with Unity. If you've installed Unity in the default location, the build will be able to find them automatically. If not, copy these DLLs from `Unity/Editor/Data/Managed` into the `lib` directory in order for the build to work.
 
 ### Visual Studio
 
-To build with Visual Studio 2015 open the solution file `GitHub.Unity.sln`. Select `Build Solution` in the `Build` menu.
+To build with Visual Studio 2015+ open the solution file `GitHub.Unity.sln`. Select `Build Solution` in the `Build` menu.
 
 ### Mono and Bash (windows and mac)