code: public EntryStream<K, V> prepend(Map<K, V> map) {
          return prependSpliterator(null, map.entrySet().spliterator());
      }
docs: Returns a new {@code EntryStream} which is a concatenation of the stream
  created from the supplied map entries and this stream.
  
  <p>
  This is a <a href="package-summary.html#StreamOps">quasi-intermediate
  operation</a> with <a href="package-summary.html#TSO">tail-stream
  optimization</a>.
  
  <p>
  May return this if the supplied map is empty and non-concurrent.
  
  @param map the map to prepend to the stream
  @return the new stream
  @since 0.2.1