Rephrase the hibernate explanation.

README.md

@@ -85,6 +85,7 @@ If you want to compile the kernel yourself (e.g. if your distribution is not sup
 
 * If you are getting stuck at boot when loading the ramdisk, you need to install the Processor Microcode Firmware for Intel CPUs (usually found under Additional Drivers in Software and Updates).
 * Do not install TLP! It can cause slowdowns, laggy performance, and occasional hangs! You have been warned.
+* If you want to use hibernate instead of suspend, you need to create a swap partition or file, please follow your distribution's instructions (or [here][hibernate-setup]).
 
 ### Support