Report the type and value that generated the error

toml.go

diff --git a/toml.go b/toml.go
index 8cf77d6..2c43d73 100644
--- a/toml.go
+++ b/toml.go
@@ -221,8 +221,8 @@
 		case *TomlTree:
 			subtree = node
 		default:
-			return fmt.Errorf("unknown type for path %s (%s)",
-				strings.Join(keys, "."), intermediateKey)
+			return fmt.Errorf("unknown type for path %s (%s): %T (%#v)",
+				strings.Join(keys, "."), intermediateKey, nextTree, nextTree)
 		}
 	}
 	return nil