If you encounter an error when you tried to install Unity, such as "'WSA' does not exist in UnityEngine.VR", this means that you need to install the Unity Editor first! http://unity3d.com/pages/windows/hololens
Run as Adminstrator on this UnitySetup64(1) - 311 MB
C:\Program Files\Unity Hololens 5.4.0b10-HTP\
Then you can install the UWP runtime: Install UnitySetup-Metro-Support-for-Editor-5.4.0b10-HTP
Finally, there is HoloLens Emulator. Although the requirement for installation is Windows 7 SP 1, it is useless since VS 2015 is unable to run the HoloLens emulator if your OS is not Windows 10.