title: Angular2: ng2-img-cropper does not crop url image
body: <p>I am using ng2-img-cropper to crop a photo (not avatar). 
  <a href="https://github.com/cstefanache/angular2-img-cropper" rel="nofollow noreferrer">https://github.com/cstefanache/angular2-img-cropper</a></p>
  
  <p>I followed the example:
  <a href="https://embed.plnkr.co/V91mKCNkBQZB5QO2MUP4/" rel="nofollow noreferrer">https://embed.plnkr.co/V91mKCNkBQZB5QO2MUP4/</a></p>
  
  <p>I saw that it seems not to support url image, only local image. Is there anyway to make it work with url image?</p>
  
  <p>If not, is there any alternative which can work with url image?</p>
  
  <p>Thanks for any suggestion.</p>