Configuration File for user defaults

[jhunt]

hatop should search through the filesystem for an optional .hatop/config file that defines defaults for command-line arguments that may have to regularly be supplied.

For example, I have a couple of places where the haproxy socket is in a non-standard location, and I regularly have to pass the --unix-socket CLI arg. I would much prefer to have this:

$ cat ~/.hatop/config
unix-socket=/my/weird/haproxy.sock

and then never have to specify the flag (on that box, at least) ever again.

Inspired by feurix/hatop#5