[ubuntu] warning boot volume low free up disk space topic

it is saying their is little space remaining in "boot" I tried gparted to make boot bigger but it does not let me do anything so what do I use to fix this problem?
it tells me to remove unused programs or files but can I move files out of boot? dont want to bugger things up by doing that would that be safe to do?

using windows 8 and ubuntu 14.04 and duel booting setup...