couchdb 2.0 uses port 5986 for _stats endpoint

[javamonn]

Clustering was introduced in CouchDB 2.0, and the _stats endpoint no longer exists at the cluster level, i.e. http://couchdb-host:5984/_stats will 404. _stats is a "node level" API and is now accessible at http://couchdb-host:5986/_stats. Some sparse documentation of this exists here and a discussion relating to this issue here.

Perhaps it makes sense to update the default couchdb.conf template to use http://localhost:5986/_stats or to notate the different port for installation on 2.0? This was the only change I had to make to use the monitoring plugin with CouchDB 2.0. I can PR this if it would be accepted.

[igorpeshansky]

Thanks. Please feel free to send a PR after signing the CLA. It's probably best to add a separate couchdb-2.conf file. Also note that these configs are generated from Jinja templates, so you'd want to include two commits into the PR -- one for adding the new template, and the other with the generated file (see #36 for an example).