Update readme with NaCl info

README.md

@@ -27,7 +27,8 @@ Moonlight also has mobile versions for [Android](https://github.com/moonlight-st
 * Chrome browser on Windows, Mac OS X, Linux, or Chrome OS
 * [GameStream-compatible](http://shield.nvidia.com/play-pc-games/) computer with GTX 600+ series desktop or mobile GPU (for the PC from which you're streaming)
 * High-end wireless router (802.11n dual-band recommended) or wired network
-* Hardware acceleration enabled under `chrome://settings`
+* Hardware acceleration enabled under `chrome://settings/system`
+* For Linux users, ensure your Chrome/Chromium package was built with NaCl support. Google's official packages are, but your distro's packages may not be.
 
 ## Building
 1. Install the Chrome Native Client SDK and download the current Pepper SDK