remove fn.compact() method

It's useless. There is no way a Zepto collection can contain
`null` or `undefined` in the first place.

README.rdoc

@@ -89,9 +89,6 @@ Context and .find calls are equivalent:
     return property for each element
     e.g. pluck('innerHTML') returns an array of all innerHTML properties of all elements found
 
-  compact():
-    remove all null or undefined elements from list of elements found
-
   anim(transform, opacity, duration):
     use -webkit-transform/opacity and do an animation
 

src/zepto.js

@@ -31,12 +31,12 @@ var Zepto = (function() {
     else {
       var dom;
       if (selector instanceof Z) dom = selector.dom;
-      else if (selector instanceof Array) dom = selector;
+      else if (selector instanceof Array) dom = compact(selector);
       else if (selector instanceof Element || selector === window) dom = [selector];
       else if (fragmentRE.test(selector)) dom = fragment(selector);
       else dom = $$(document, selector);
 
-      return new Z(compact(dom), selector);
+      return new Z(dom, selector);
     }
   }
 
@@ -47,7 +47,6 @@ var Zepto = (function() {
     ready: function(callback){
       document.addEventListener('DOMContentLoaded', callback, false); return this;
     },
-    compact: function(){ this.dom = compact(this.dom); return this },
     get: function(idx){ return idx === undefined ? this.dom : this.dom[idx] },
     size: function(){ return this.length },
     remove: function(){

test/zepto.html

@@ -260,14 +260,6 @@ <h1>Zepto DOM unit tests</h1>
         t.assertLength(0, $('nonexistent').last());
       },
 
-      testCompact: function(t){
-        var nodes = $('p');
-        nodes.dom = [nodes.get(0), null, undefined, nodes.get(0)];
-        nodes.compact();
-        t.assertLength(2, nodes);
-        t.assertEqual('PP', nodes.pluck('tagName').join(''));
-      },
-
       testPluck: function(t){
         t.assertEqual('H1DIVDIV', $('h1,div.htmltest').pluck('tagName').join(''));
       },