Updated README file to add git clone with submodule instructions

README.md

-# Unity Scriptable Render Loop testbed
+# Unity Scriptable Render Pipeline testbed
 
 **NOTE**: this is a testbed for a Unity feature that has not shipped yet! The latest commits in this project does not work
 with any public Unity version, and things in it might and will be broken.
 
 Did we mention it's a very WIP, no promises, may or might not ship feature, anything and everything in it can change? It totally is.
 
+## For Unity 2017.1 beta users
+SRP depends on PostProcessing submodule. Perform the following instructions to get a working copy of SRP:
+git clone https://github.com/Unity-Technologies/ScriptableRenderLoop
+git checkout unity-2017.1b5 (or the latest tag)
+git submodule update --init --recursive
 
 ## For Unity 5.6 beta users