Add workaround for Node < 4 support with v4.x

TROUBLESHOOTING.md

@@ -16,6 +16,7 @@ This document covers some common node-sass issues and how to resolve them. You s
     - [Windows](#windows)
     - [Linux/OSX](#linuxosx)
 - [Using node-sass with Visual Studio 2015 Task Runner.](#using-node-sass-with-visual-studio-2015-task-runner)
+- [Installing node-sass 4.x with Node < 4](#installing-node-sass-4x-with-node--4)
 
 ## Installation problems
 
@@ -254,3 +255,7 @@ If this still produces an error please open an issue with the output from these
 If you are using node-sass with VS2015 Task Runner Explorer, you need to make sure that the version of node.js (or io.js) is same as the one you installed node-sass with. This is because for each node.js runtime modules version (`node -p process.versions.modules`), we have a separate build of native binary. See [#532](https://github.com/sass/node-sass/issues/532).
 
 Alternatively, if you prefer using system-installed node.js (supposedly higher version than one bundles with VS2015), you may want to point Visual Studio 2015 to use it for task runner jobs by following the guidelines available at: http://blogs.msdn.com/b/webdev/archive/2015/03/19/customize-external-web-tools-in-visual-studio-2015.aspx.
+
+### Installing node-sass 4.x with Node < 4
+
+See the discussion in [this comment](https://github.com/sass/node-sass/issues/2100#issuecomment-334651235) for a workaround. As of node-sass@v5 only Node 6 and above will be offically supported.