title: Allow zero, allow number, and maximum two number after point
body: <p>I need to write regex validation.<br/>
  Accepted numbers:<br/>
  0<br/>
  0.3<br/>
  0.21<br/>
  78.21<br/>
  8934<br/></p>
  <p>Not Allowed:<br/>
  00<br/>
  0.323<br/>
  -1<br/>
  021</p>
  <pre><code>^(?:0,\d\d|[1-9]\d*(?:,\d\d)?|)$
  </code></pre>
  <p>I had that regex, but it doesn't accept '0', and number '0.2'.</p>