Add type option, add a REDIS_KEY env variable

[warwickp]

Hey Dan

Woodchuck is great, thanks. I don't expect you will merge this, but I wanted to get your feedback anyway. Sounds like you have a configuration feature on the horizon.

This allows passing a 'type' option but doesn't make complete sense as is because type should be per path not global.

Also adds the ability to use a REDIS_KEY so you can define something other than 'namespace:events'.

I'm using this with multiple woodchucks running, 1 per type.

Also: no tests because I couldn't get the existing tests to pass anyway + laziness.

[danryan]

Nice, thanks for the updates! I'll review these and merge 'em up. Cheers :)

[danryan]

I still need to refactor woodchuck use logstash's own plugins, so this type option will actually be used quite a bit :)