Smile environment fixes.

- Don't set the default environment variable to the dev environment
  (don't set them at all).
- The default AWS profile should be smile-security, it's the one I use
  to assume roles in the other accounts.
- Set the VAULT_CAPATH to the CA files in the smile-cli gem where they
  currently are.
- Run vault login before executing commands in smile-exec. Maybe
  overkill to run it before every command, maybe I'll add an alias for
that. We'll see.