message: Removed useless counting_writer
diff: @@ -2,7 +2,6 @@ use compression::{BlockDecoder, CompressedIntStream, VIntDecoder, COMPRESSION_BL
  use DocId;
  use common::BitSet;
  -use common::CountingWriter;
  use common::HasLen;
  use compression::compressed_block_size;
  use directory::ReadOnlySource;
  @@ -79,9 +78,9 @@ impl SegmentPostings {
  /// and returns a `SegmentPostings` object that embeds a
  /// buffer with the serialized data.
  pub fn create_from_docs(docs: &[u32]) -> SegmentPostings {
  - let mut counting_writer = CountingWriter::wrap(Vec::new());
  + let mut buffer = Vec::new();
  {
  - let mut postings_serializer = PostingsSerializer::new(&mut counting_writer, false);
  + let mut postings_serializer = PostingsSerializer::new(&mut buffer, false);
  for &doc in docs {
  postings_serializer.write_doc(doc, 1u32).unwrap();
  }
  @@ -89,9 +88,7 @@ impl SegmentPostings {
  .close_term()
  .expect("In memory Serialization should never fail.");
  }
  - let (buffer, _) = counting_writer
  - .finish()
  - .expect("Serializing in a buffer should never fail.");
  +
  let data = ReadOnlySource::from(buffer);
  let block_segment_postings = BlockSegmentPostings::from_data(
  docs.len(),
  