Fix different reuslts on duplicate keys

fixes #79

gjson.go

@@ -383,9 +383,13 @@ func (t Result) arrayOrMap(vc byte, valueize bool) (r arrayOrMapResult) {
 				key = value
 			} else {
 				if valueize {
-					r.oi[key.Str] = value.Value()
+					if _, ok := r.oi[key.Str]; !ok {
+						r.oi[key.Str] = value.Value()
+					}
 				} else {
-					r.o[key.Str] = value
+					if _, ok := r.o[key.Str]; !ok {
+						r.o[key.Str] = value
+					}
 				}
 			}
 			count++

gjson_test.go

@@ -1391,3 +1391,18 @@ func TestNumFloatString(t *testing.T) {
 		t.Fatalf("expected '%v', got '%v'", "-9007199254740993", res.String())
 	}
 }
+
+func TestDuplicateKeys(t *testing.T) {
+	// this is vaild json according to the JSON spec
+	var json = `{"name": "Alex","name": "Peter"}`
+	if Parse(json).Get("name").String() !=
+		Parse(json).Map()["name"].String() {
+		t.Fatalf("expected '%v', got '%v'",
+			Parse(json).Get("name").String(),
+			Parse(json).Map()["name"].String(),
+		)
+	}
+	if !Valid(json) {
+		t.Fatal("should be valid")
+	}
+}