Fix Marshal examples (#178)

* Fix Marshal examples
* Move ExampleMarshal to doc test

marshal_test.go

@@ -177,25 +177,6 @@ func TestDocUnmarshal(t *testing.T) {
 	}
 }
 
-func ExampleUnmarshal() {
-	type Postgres struct {
-		User     string
-		Password string
-	}
-	type Config struct {
-		Postgres Postgres
-	}
-
-	doc := []byte(`
-	[postgres]
-	user = "pelletier"
-	password = "mypassword"`)
-
-	config := Config{}
-	Unmarshal(doc, &config)
-	fmt.Println("user=", config.Postgres.User)
-}
-
 func TestDocPartialUnmarshal(t *testing.T) {
 	result := testDocSubs{}