- Fix corrupted data for concatenated bzip2 streams in one bzip2 file in serial BZ2Reader.
 - Add C++17 threaded parallel bzip2 block decoder which is used when constructing
   'IndexedBzip2File' with argument 'parallelization' != 1.
 - Provide readline, readlines, peek methods by inheriting from BufferedReader.
 - Add available_block_offsets, block_offsets_complete, and size method.
 - Do not build index when seeking to current position.