feature(SIGUSR2): SIGUSR2 sets loglevel EVERYTHING
fix(log): Call the log function properly
fix(signal handling): Don't send duplicate signals

- With this code, all signals were being recieved twice. Reading docs
  here: http://nikhilm.github.io/uvbook/processes.html#signals it seems
  we only need to listen for signals once, and that's already done
  inside libuv directly.
- Also added logging to all other signal handlers for ease of
  troubleshooting.
Merge pull request #30 from racker/jay/LogEverythingOnUSR2

feature(SIGUSR2): SIGUSR2 sets loglevel EVERYTHING