title: Add new shape on paper(Raphael JS)
body: <p>i need to add new shape to papaer object using button. 
  my html:</p>
  
  <pre><code>&lt;html&gt;
      &lt;head&gt;
          &lt;title&gt;Calculator&lt;/title&gt;
          &lt;script type="text/javascript" src="raphael.js"&gt;&lt;/script&gt;
          &lt;script type="text/javascript" src="calc.js"&gt;&lt;/script&gt;
          &lt;style type="text/css"&gt;
              #canvas_container {
                  width: 500px;
                  height: 300px;
                  border: 1px solid #aaa;
                  background-color: #cacaca;
              }
          &lt;/style&gt;
      &lt;/head&gt;
      &lt;body&gt;
          &lt;div id="canvas_container"&gt;&lt;/div&gt;
  
          &lt;FORM NAME="myform" ACTION="" METHOD="GET"&gt;
          Width:
          &lt;INPUT TYPE="text" NAME="width" VALUE=""&gt;
          &lt;INPUT TYPE="button" NAME="button" Value="Click" onClick="testResults(this.form)"&gt;
          &lt;/FORM&gt;
  
      &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>my calc.js is:</p>
  
  <pre><code>window.onload = function() {
  
  }
  
  function testResults (form){
  var paper = new Raphael(document.getElementById('canvas_container'), 500, 500);
      var small = paper.path("M10 270 L 60 270 M10 265 L 10 275 M60 265 L60 275");
      var txtbig = paper.text(230, 210, form.width.value+" m");
  
      var big = paper.path("M10 200 L 480 200");
      var txtsmall = paper.text(30, 280, ((form.width.value)*50/470).toFixed(2)+" m");
  }
  </code></pre>
  
  <p>How can i add new shape (for example rectangle) using a button?
  Or how to add/remove shape using checkbox. 
  What i dont know how to do is how to call paper object using another function.</p>
  
  <p>Hope it's clear and you can help me!</p>