expose the file(s) config was taken from.

[dominictarr]

When you pass in the --config option, the application will know the file
the config was loaded from. This could be useful for 1) updating config programatically, and 2) looking relative to the config file, i.e. for ssl keys.

it could be an array of file names in the override order. (first is local config, etc)

[mikermcneil]

Just ran into a use case where this would be helpful-- seems like it would be hard to do w/o changing the way rc works though.. maybe I'll make a modified version or wrapper? Thoughts?

[dbkaplun]

This issue should be closed as of 0971fc3.