code: public static RequestToken fetch(String collection, String id,boolean withAcl, BaasHandler<BaasDocument> handler) {
          return doFetch(collection, id, withAcl, RequestOptions.DEFAULT, handler);
      }
docs: Asynchronously fetches the document identified by <code>id</code> in <code>collection</code>
  
  @param collection the collection to retrieve the document from. Not <code>null</code>
  @param id         the id of the document to retrieve. Not <code>null</code>
  @param withAcl if true will fetch acl
  @param handler    a callback to be invoked with the result of the request
  @return a {@link com.baasbox.android.RequestToken} to handle the asynchronous request