Add gitignore
parse_wakeup_source: pass in function pointer as iterator callback
Read wakeup_sources on each iteration
policy: Simple hardcoded timeout

Hard-coded policy waits until a hard-coded time after the last wakeup event.
Don't use file streams for wakeup_count

I don't get the return value from the write system call back directly.
Turns out getting the count value as an integer wasn't necessary anyway,
so just keep it as a string which is simple with read()/write().
Add systemd service file
Implement hysteresis command line option
Allow configuring log levels