Allow setting user and group ownership of rendered templates

[Chili-Man]

Currently, consul-template does not allow changing the user/group ownership of the rendered templates. This does not permit allowing only specific users/groups to read from the rendered templates. As a workaround, one can launch a consul-template as a specific user for each template to be rendered, but it is not ideal as you would have to possibly launch many consul-template processes.

[sethvargo]

Hi @Chili-Man

Thank you for opening an issue. This is a duplicate of #461, please see the comments on that issue. Thanks! 😄