add Path.parent() and Path.last() methods

Neither is very efficient, but we'll live.

src/main/java/com/typesafe/config/impl/Path.java

@@ -53,10 +53,43 @@ final class Path {
         return first;
     }
 
+    /**
+     *
+     * @return path minus the first element or null if no more elements
+     */
     Path remainder() {
         return remainder;
     }
 
+    /**
+     *
+     * @return path minus the last element or null if we have just one element
+     */
+    Path parent() {
+        if (remainder == null)
+            return null;
+
+        PathBuilder pb = new PathBuilder();
+        Path p = this;
+        while (p.remainder != null) {
+            pb.appendKey(p.first);
+            p = p.remainder;
+        }
+        return pb.result();
+    }
+
+    /**
+     *
+     * @return last element in the path
+     */
+    String last() {
+        Path p = this;
+        while (p.remainder != null) {
+            p = p.remainder;
+        }
+        return p.first;
+    }
+
     Path prepend(Path toPrepend) {
         PathBuilder pb = new PathBuilder();
         pb.appendPath(toPrepend);

src/test/scala/com/typesafe/config/impl/PathTest.scala

@@ -64,6 +64,19 @@ class PathTest extends TestUtils {
         assertEquals(2, path("foo", "bar").length())
     }
 
+    @Test
+    def pathParent() {
+        assertNull(path("a").parent())
+        assertEquals(path("a"), path("a", "b").parent())
+        assertEquals(path("a", "b"), path("a", "b", "c").parent())
+    }
+
+    @Test
+    def pathLast() {
+        assertEquals("a", path("a").last())
+        assertEquals("b", path("a", "b").last())
+    }
+
     @Test
     def pathsAreInvalid() {
         // this test is just of the Path.newPath() wrapper, the extensive