Start with a slice large enough for the minimum version

Closes #12

semver.go

@@ -30,7 +30,7 @@ type Version struct {
 
 // Version to string
 func (v Version) String() string {
-	b := make([]byte, 0)
+	b := make([]byte, 0, 5)
 	b = strconv.AppendUint(b, v.Major, 10)
 	b = append(b, '.')
 	b = strconv.AppendUint(b, v.Minor, 10)

semver_test.go

@@ -301,6 +301,16 @@ func BenchmarkStringSimple(b *testing.B) {
 	}
 }
 
+func BenchmarkStringLarger(b *testing.B) {
+	const VERSION = "11.15.2012"
+	v, _ := New(VERSION)
+	b.ReportAllocs()
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		v.String()
+	}
+}
+
 func BenchmarkStringComplex(b *testing.B) {
 	const VERSION = "0.0.1-alpha.preview+123.456"
 	v, _ := New(VERSION)