fix #708, inherit umask when daemonizing

The main flapjack log is hardwired `0644` in `dante` itself, which I didn't want to hack around any more than it already is -- if this is an issue we'll need to do our own redirection of stdout/stderr and skip dante's logging completely, which is a fair bit of work for some functionality we'll hopefully be throwing away shortly. Other logs should now inherit the parent process starting environmental umask though.

I've locked the `dante` version in the gemspec as we're already redefining methods from it to avoid some things it breaks for us.