Add windows splunk forwarder

Added logic for installing forwarder on windows.

Fixes #4 
A couple of notes here. I think we should leave off the `start_from` and `current_only` attributes (at least have the first one without either, so people can copy and paste an example). The `start_from` attribute defaults to `'oldest'` therefore specifying it as such feels redundant. With regards to `current_only,` while there may be cases where we'd want to turn this on (likely temporarily only), more often than not we should have this off so that we don't miss events from restarts of Splunk.