Update benchmark (go1.13)

Author: timonwong

README.md

@@ -64,28 +64,29 @@ Comparision with the standard library `time.(*Time).Format()`:
 goos: darwin
 goarch: amd64
 pkg: github.com/imperfectgo/go-strftime
-BenchmarkStdTimeFormat-4         5000000               356 ns/op              48 B/op          1 allocs/op
-BenchmarkGoStrftime-4            5000000               347 ns/op              32 B/op          1 allocs/op
+BenchmarkStdTimeFormat-4         3844191               315 ns/op              32 B/op          1 allocs/op
+BenchmarkGoStrftime-4            4354848               274 ns/op               0 B/op          0 allocs/op
 PASS
-ok      github.com/imperfectgo/go-strftime      4.245s
+ok      github.com/imperfectgo/go-strftime      3.013s
 ```
 
 Comparision with other libraries:
 
 ```
-> go test -tags benchcomp -bench Bench -cpu 8 -benchmem .
+> go test -tags benchcomp -bench Bench -cpu 4 -benchmem .
 
 goos: darwin
 goarch: amd64
-pkg: github.com/imperfectgo/go-strftime/benchmark
-BenchmarkImperfectGo-8                   3000000               484 ns/op              64 B/op          1 allocs/op
-BenchmarkTebeka-8                         300000              4161 ns/op             272 B/op         20 allocs/op
-BenchmarkJehiah-8                        1000000              1719 ns/op             256 B/op         17 allocs/op
-BenchmarkFastly-8                        2000000               708 ns/op              85 B/op          5 allocs/op
-BenchmarkLestrrat-8                      1000000              1471 ns/op             240 B/op          3 allocs/op
-BenchmarkLestrratCachedString-8          3000000               496 ns/op             128 B/op          2 allocs/op
+pkg: github.com/imperfectgo/go-strftime
+BenchmarkImperfectGo-4                   2713639               445 ns/op              64 B/op          1 allocs/op
+BenchmarkImperfectGoNoAlloc-4            3081366               389 ns/op               0 B/op          0 allocs/op
+BenchmarkTebeka-4                         311500              3930 ns/op             256 B/op         19 allocs/op
+BenchmarkJehiah-4                         712195              1709 ns/op             256 B/op         17 allocs/op
+BenchmarkFastly-4                        1934066               615 ns/op              80 B/op          5 allocs/op
+BenchmarkLestrrat-4                      1000000              1037 ns/op             240 B/op          3 allocs/op
+BenchmarkLestrratCachedString-4          2415724               498 ns/op             128 B/op          2 allocs/op
 PASS
-ok      github.com/imperfectgo/go-strftime/benchmark    10.605s
+ok      github.com/imperfectgo/go-strftime      10.332s
 ```
 
 ## License

benchmark_comp_test.go

@@ -29,6 +29,13 @@ func BenchmarkImperfectGo(b *testing.B) {
 	}
 }
 
+func BenchmarkImperfectGoNoAlloc(b *testing.B) {
+	var buf [128]byte
+	for i := 0; i < b.N; i++ {
+		imperfectgo.AppendFormat(buf[:0], now, benchfmt)
+	}
+}
+
 func BenchmarkTebeka(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		tebeka.Format(benchfmt, now)