Remove subpath, reuse path.

Looks like the end of obvious minzip savings in the interpreter.

See #46.

File                             Raw         Min         Zip     Min/Zip
index.js                  5452/05.32  2018/01.97  1809/01.77   978/00.96

index.js

@@ -83,8 +83,8 @@
           } else if (nameOrPredicate == '.') {
             candidates.push(candidate);
           } else if (nameOrPredicate == '..') {
-            var subpath = path.slice();
-            candidates.unshift({ o: subpath.shift(), p: subpath, i: 0 });
+            path = path.slice();
+            candidates.unshift({ o: path.shift(), p: path, i: 0 });
           } else if (Array.isArray(object)) {
             for (j = object.length - 1; j > -1; --j) {
               stack.unshift({ o: object[j], p: [ object ].concat(path) });