title: Qunit PropEqual but in Chai
body: <p>I am looking to compare properties of an object but I am moving to mocha away from QUnit and I was wondering if there was a chai equivalent of propEqual:</p>
  
  <p>Example of that I need in chai:</p>
  
  <pre><code>QUnit.test( "propEqual test", function( assert ) {
    function Foo( x, y, z ) {
      this.x = x;
      this.y = y;
      this.z = z;
    }
    Foo.prototype.doA = function () {};
    Foo.prototype.doB = function () {};
    Foo.prototype.bar = 'prototype';
  
    var foo = new Foo( 1, "2", [] );
    var bar = {
      x : 1,
      y : "2",
      z : []
    };
    assert.propEqual( foo, bar, "Strictly the same properties without comparing objects constructors." );
  });
  </code></pre>