Account.key path is not created when using acme reg -gen

[frederik256]

When using the command:
c:\Acme> acme reg -gen mailto:someuser@random.org"

it throws an error
account key: open C:\Users\myusername\.config\acme\account.key: The system cannot find the path specified.

when the .config directory does not exist.
This is on Windows 10, with the 1.1.1 binary.

Workaround: create directories manually.
Fix: automatically create directories .config and .config/acme if they dont' exist.

[bof]

The (open) pull request #56 might fix that (change to first file there, the other is a nicer error message for a different case).

Not tested on windows, though, but it sounds like the same issue.