Various feature additions

[StephenWattam]

I figured you might want this bunch of edits. There's a few features in there:

• Handling of signals (they are passed through to the child process)
• Runtime configuration of poll rate
• Stricter flushing of files when writing output
• A modification to the hashbang line to facilitate the flushing behaviour above
• Support for -h to show usage info

Thanks!
-- Steve