Extend Metrics with max and 95th, 99th percentiles

Implements a new format for the text reporter with more information
than before.
Also Rename Result.Timing to Result.Latency and related names.
Adapt README.md examples to account new text reporter format and
library changes.

lib/results.go

@@ -12,7 +12,7 @@ import (
 type Result struct {
 	Code      uint16
 	Timestamp time.Time
-	Timing    time.Duration
+	Latency   time.Duration
 	BytesOut  uint64
 	BytesIn   uint64
 	Error     string