async/src/main/java/com/stanfy/enroscar/async/Tools.java
public static <D> Async<D> async(final Callable<D> task) {
    return async(null, task);
  }
public static <D> Async<D> async(final Callable<D> task) {
    return async(null, task);
  }
Create an asynchronous operation that executes a provided task creating
an Android's {@link android.os.AsyncTask}.
@param task job to do
@param <D> result data type
@return implementation of {@link Async}, never {@code null}