feat: add protocol option

[ljun20160606]

#2152

[monkey92t]

Good!

[monkey92t]

Oh~ We forgot about ParseClusterURL in cluster.go. Can you send another PR to include it? @ljun20160606

go-redis/cluster.go

Lines 217 to 236 in 3917988

	func setupClusterQueryParams(u *url.URL, o *ClusterOptions) (*ClusterOptions, error) {
	q := queryOptions{q: u.Query()}
	o.ClientName = q.string("client_name")
	o.MaxRedirects = q.int("max_redirects")
	o.ReadOnly = q.bool("read_only")
	o.RouteByLatency = q.bool("route_by_latency")
	o.RouteRandomly = q.bool("route_randomly")
	o.MaxRetries = q.int("max_retries")
	o.MinRetryBackoff = q.duration("min_retry_backoff")
	o.MaxRetryBackoff = q.duration("max_retry_backoff")
	o.DialTimeout = q.duration("dial_timeout")
	o.ReadTimeout = q.duration("read_timeout")
	o.WriteTimeout = q.duration("write_timeout")
	o.PoolFIFO = q.bool("pool_fifo")
	o.PoolSize = q.int("pool_size")
	o.MinIdleConns = q.int("min_idle_conns")
	o.PoolTimeout = q.duration("pool_timeout")
	o.ConnMaxLifetime = q.duration("conn_max_lifetime")
	o.ConnMaxIdleTime = q.duration("conn_max_idle_time")

[ljun20160606]

setupClusterQueryParams

Of course, I'm going to add it tomorrow.