HTC One M8 stuck on start up screen after SuperSU update

[AC Question]

I have a HTC One M8, it has been telling me for weeks that my SiperSU app needed updating but I did not have enough memory so I cleared some apps I don't use and updated it last night. It said it needed to reboot to finish installation but when it turned back on it is stuck on the HTC One white start up screen. I have tried turning it off with the hardware buttons but it just loads back on to the white screen and gets stuck again. Please help!!