Add remote (SSH) metrics interface gathering

[CoRfr]

Pull Request Checklist

Is this in reference to an existing issue?

General

• [x] Update Changelog following the conventions laid out here

• [x] Update README with any necessary configuration snippets

• [x] Binstubs are created if needed

• [x] RuboCop passes

• [x] Existing tests pass

New Plugins

• [ ] Tests

• [x] Add the plugin to the README

• [x] Does it have a complete header as outlined here

Purpose

This script, very similar to metrics-interface.rb, allows to collect
metrics on remote host by SSH.

This is meant to be able to collect metrics on host that cannot
necessarily run sensu client, such as small routers for instance.

Known Compatibility Issues

[CoRfr]

Do you mean adding excludeinterfaceregex/includeinterfaceregex ?

[jindraj]

Do you mean adding excludeinterfaceregex/includeinterfaceregex ?

thank you

[jspaleta]

Hey, Can you take a look and see if this PR is still relevant. If it is can you rebase against master so we can get the travisCI happy?

If this is not still needed, please close.

[CoRfr]

@jspaleta , I would think it's still relevant so I merged the master branch into this commit to update it, and resolved conflicts accordingly. Thanks !