Have `parseUrl` handle unix domain sockets

[blaggacao]

Motivation

Currently parseUrl is an incomplete parser of the url subset of connection strings, ommiting support for the otherwise supportes unix domain socket connection.

As a connection string parser, it is not clear why it should be limited to URLs only and this seems like a debt to legacy code rather than an intended design decision.

Making unix domain socket connection strings harder to work with discourages their use.

Basic Code Example

/*
  unix://[user:secret@]/path/to/sock[?db=0]
  redis://[user:secret@]localhost:6379/0
  rediss://[user:secret@]localhost:6379/0
*/
client = redis.createClient({ url: connStr, ...options });

See redis-py support