Permissions of .iron files should be more restrictive

[clintfred]

I would like the permissions of the files in ~/.iron to be more restrictive, so that other users on a shared system would have a harder time seeing my device keys.

I am on Linux, and I think good permissions would be 600. I'm not sure how that would work in Windows, if you are supporting that.
Maybe everything in .iron could always be created with these restricted permissions? The most important one to me is .iron/keys.

[skeet70]

600 seems like what it should be, this would be a pretty easy issue for someone to tackle.