force all linux cpu stats to be between 0 and 100.

on our 1500 nodes running rhel6 kernels we get a few of these daily:
  cpu_wio_func: val > 100: 1.15299e+17 ~ 1.84467e+19 / 15999 = (3051596 - 3051599) / (902933030 - 902917031)
which are caused by negative rates from /proc/stat being cast to unsigned.
usually it's cpu_wio_func, but we also see it with cpu_idle_func and cpu_user_func.

this patch range limits all linux cpu stats to 0 -> 100 and stops the huge spikes in ganglia data.
obviously it's not solving the core of the problem (it could be the kernel or ganglia), but either way it's much better than spikes.
Merge pull request #76 from plaguedbypenguins/master

limit linux cpu stats to [0,100] to remove huge spikes