Address keybase/keybase-issues#227

Better support for users with `secret-keyring` off on an external device. In practice,
this means that we have to touch the temporary `secring.gpg` before we can import to it,
a constraint which isn't enforced if `secret-keyring` isn't specified in the `gpg.conf` file.
Merge branch 'master' of github.com:keybase/gpg-wrapper

Conflicts:
	CHANGELOG.md
	lib/keyring.js