Flash SuperSU, then fastboot flash this boot.img, then you have root.
hi click me
EDIT: Gather round guys.
Lots of you are complaining that apps like titanium backup and helium are crashing or just not working. And the popular thing to do is complain that there is no /system write access, buuuut, there is system write access. I'll admit it, at first instinct I thought this was the case too. Upon further inspection, it looks like root app developers are going to need to the new security contexts when they run an elevated command. This will explain why some of your apps can write to system and some cannot. I know Root Explorer has been properly updated, for example. If you'd like to read up more, check this link out
. Credit to @Chainfire
for the bits n bolts.
Now that that's cleared up, here's a flo boot.img
I don't have it, but the method was the same, give it a swing.