Scan /proc/[pid]/{io,stat,status} as required to generate per process
stats

SHH_PROCESSES_REGEX determines which processes get scanned

temporary until we use cgo there is SHH_TICKS and SHH_PAGESIZE, defaults
should be find though for linux/x86 systems
if we can't read the file, don't try to submit a measurement
Merge pull request #30 from heroku/track_processes

Track processes