Add M3 machine types to validMachineTypes (#233)

Author: wata727

rules/utils.go

@@ -147,6 +147,11 @@ var validMachineTypes = map[string]bool{
 	"c2d-highcpu-32":   true,
 	"c2d-highcpu-56":   true,
 	"c2d-highcpu-112":  true,
+	"m3-megamem-64":    true,
+	"m3-megamem-128":   true,
+	"m3-ultramem-32":   true,
+	"m3-ultramem-64":   true,
+	"m3-ultramem-128":  true,
 	"m2-ultramem-208":  true,
 	"m2-ultramem-416":  true,
 	"m2-megamem-416":   true,