Update readme examples with the new API

Author: Joris-van-der-Wel

README.md

@@ -18,15 +18,15 @@ let a = {foo: 'bar'}; // or `new Whatever()`
 let b = {foo: 'baz'};
 let c = {foo: 'qux'};
 
-tree.insertBefore(a, b); // insert a before b
-tree.insertAfter(c, b); // insert c after b
+tree.insertBefore(b, a); // insert a before b
+tree.insertAfter(b, c); // insert c after b
 
-console.log(tree.next(a) === b);
-console.log(tree.next(b) === c);
-console.log(tree.prev(c) === b);
+console.log(tree.nextSibling(a) === b);
+console.log(tree.nextSibling(b) === c);
+console.log(tree.previousSibling(c) === b);
 
 tree.remove(b);
-console.log(tree.next(a) === c);
+console.log(tree.nextSibling(a) === c);
 ```
 
 A tree:
@@ -40,17 +40,17 @@ let a = {};
 let b = {};
 let c = {};
 
-tree.insertFirst(a, parent); // insert a as the first child
-tree.insertLast(c, parent); // insert c as the last child
-tree.insertAfter(b, a); // insert b after a, it now has the same parent as a
+tree.prependChild(parent, a); // insert a as the first child
+tree.appendChild(parent,c ); // insert c as the last child
+tree.insertAfter(a, b); // insert b after a, it now has the same parent as a
 
-console.log(tree.first(parent) === a);
-console.log(tree.next(tree.first(parent)) === b);
-console.log(tree.last(parent) === c);
+console.log(tree.firstChild(parent) === a);
+console.log(tree.nextSibling(tree.firstChild(parent)) === b);
+console.log(tree.lastChild(parent) === c);
 
 let grandparent = {};
-tree.insertFirst(parent, grandparent);
-console.log(tree.first(tree.first(grandparent)) === a);
+tree.prependChild(grandparent, parent);
+console.log(tree.firstChild(tree.firstChild(grandparent)) === a);
 ```
 
 See [api.md](api.md) for more documentation.