Add some helpers for tree manipulation

src/toml/parser_test.go

@@ -0,0 +1,13 @@
+package toml
+
+import "testing"
+
+
+func testCreateSubTree(t *testing.T) {
+	tree := make(tomlTree)
+	createSubTree(&tree, "a.b.c")
+	tree.Set("a.b.c", 42)
+	if tree.Get("a.b.c") != 42 {
+		t.Fail()
+	}
+}