fmt
remove extraneous calls to log.Fatal

we should be shutting down with calls to shutdown now, to ensure our
shutdown handlers run
added test-config subcommand

usage:  `lumberjack test-config /path/to/config`
add support for network group configs

groups don't actually work yet!  This is just the updates to the config
file format.
add support for network groups
remove unused import
define options struct

it was a little weird having all those global variables floating around
for command line options, so I'm geting rid of that.
Merge pull request #11 from jorelli/master

support multiple logstash receiver groups
bumping to version 0.4.3, adding details to README.md on how multi-network setup works