Create metrics-couchdb-database.rb

[FlorinAndrei]

Pull Request Checklist

Is this in reference to an existing issue?

General

• [ ] Update Changelog following the conventions laid out on Keep A Changelog
• [ ] Update README with any necessary configuration snippets
• [ ] Binstubs are created if needed
• [ ] RuboCop passes
• [ ] Existing tests pass

  New Plugins

• [ ] Tests
• [ ] Add the plugin to the README
• [ ] Does it have a complete header as outlined here

  Purpose

  Known Compatablity Issues

Give it the name of the database, and it will return all metrics (numeric stats) associated with it, such as number of documents, sequence number, etc.

[sstarcher]

@mattyjones cert errors on this repo