title: Firebase & angular2: Can I create request for filter by value
body: <p>Can I create request to table 'User' for filter by value one field, I don't want get all record in table 'user'.
  For example: I have array.</p>
  
  <pre><code>[{email: "email1@ar.rom", password: "111"}, {email: "email2@ar.rom", password: "111"}]
  </code></pre>
  
  <p>I created request:</p>
  
  <pre><code>af: AngularFire;
  
  this.af.database.object('/users/',{
          query: {
              orderByChild: 'password',
              equalTo: '14714711'
          }
      })
  </code></pre>
  
  <p>This request get my 2 record. if want get 1 record. What my create request with filter by value 1 field?</p>