Update certificates dependency.

Update a few API calls and variables referencing certificates ssh.

Merge pull request smallstep#180 from smallstep/go-mod

Use go mod on smallstep/cli

dep update certificates

Merge pull request smallstep#156 from smallstep/okta-support

Address support on OIDC provisioners

dep update certificates

dep update certificates

dep update certificates to v0.12.0

Small change to feedback solicitation

Merge pull request smallstep#118 from smallstep/iid-common-names

Add subject to the list of SANs in cloud providers