Version 1.5.0

Added

• Add add_bytes_vectored() methods to pbf_writer and pbf_builder. This
  allows single-copy scatter-gather type adding of data that has been prepared
  in pieces to a protobuf message.
• New functions to check the tag and wire type at the same time: Two parameter
  version of pbf_reader::next() and pbf_reader::tag_and_type() can be used
  together with the free function tag_and_type() to easily and quickly check
  that not only the tag but also the wire type is correct for a field.

Changed

• packed_field_* classes now work with pbf_builder.
• Reorganized documentation. Advanced docs are now under doc/advanced.md.

Fixed

• packed_field class is now non-copyable because data can get corrupted if
  you copy it around.
• Comparison operators of data_view now have const& parameters.
• Make zigzag encoding/decoding functions constexpr.