Update README for Windows 10 support.

PR-URL: #766
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

README.md

@@ -50,6 +50,14 @@ You will also need to install:
         * If you get errors that the 64-bit compilers are not installed you may also need the [compiler update for the Windows SDK 7.1]
     * Windows 7/8:
       * Microsoft Visual Studio C++ 2013 for Windows Desktop ([Express][msvc2013] version works well)
+    * Windows 10:
+        * Install the latest version of npm (3.3.6 at the time of writing)
+        * Install Python 2.7 from https://www.python.org/download/releases/2.7/ and make sure its on the System Path
+        * Install Visual Studio Community 2015 Edition. (Custom Install, Select Visual C++ during the installation)
+        * Set the environment variable GYP_MSVS_VERSION=2015
+        * Run the command prompt as Administrator
+        * $ npm install (--msvs_version=2015) <-- Shouldn't be needed if you have set GYP_MSVS_VERSION env
+        * If the above steps have not worked or you are unsure please visit http://www.serverpals.com/blog/building-using-node-gyp-with-visual-studio-express-2015-on-windows-10-pro-x64 for a full walkthrough
     * All Windows Versions
       * For 64-bit builds of node and native modules you will _**also**_ need the [Windows 7 64-bit SDK][win7sdk]
       * You may need to run one of the following commands if your build complains about WindowsSDKDir not being set, and you are sure you have already installed the SDK: