Before this change, ParseURL would only accept a very restricted
set of URLs (it returned an error, if it encountered any parameter).
This commit introduces the ability to process URLs like
redis://localhost/1?dial_timeout=10s
and similar.
Go programs which were providing a configuration tunable (e.g.
CLI flag, config entry or environment variable) to configure
the Redis connection now don't need to perform this task
themselves.
This is in preparation for supporting query parameters
in ParseURL:
- use an expected *Options instance to execute assertions on
- extract assertions into helper function
- enable parallel testing
- condense test table