Smart-open

- Add missing boto dependency (Issue [468](https://github.com/RaRe-Technologies/smart_open/issues/468))

- Fix GCS multiple writes (PR [421](https://github.com/RaRe-Technologies/smart_open/pull/421), [petedannemann](https://github.com/petedannemann))
- Implemented efficient readline for ByteBuffer (PR [426](https://github.com/RaRe-Technologies/smart_open/pull/426), [mpenkov](https://github.com/mpenkov))
- Fix WebHDFS read method (PR [433](https://github.com/RaRe-Technologies/smart_open/pull/433), [mpenkov](https://github.com/mpenkov))
- Make S3 uploads more robust (PR [434](https://github.com/RaRe-Technologies/smart_open/pull/434), [mpenkov](https://github.com/mpenkov))
- Add pathlib monkeypatch with replacement of `pathlib.Path.open` (PR [436](https://github.com/RaRe-Technologies/smart_open/pull/436), [menshikh-iv](https://github.com/menshikh-iv))
- Fix error when calling str() or repr() on GCS SeekableBufferedInputBase (PR [442](https://github.com/RaRe-Technologies/smart_open/pull/442), [robcowie](https://github.com/robcowie))
- Move optional dependencies to extras (PR [454](https://github.com/RaRe-Technologies/smart_open/pull/454), [Amertz08](https://github.com/Amertz08))
- Correctly handle GCS paths that contain '?' char (PR [460](https://github.com/RaRe-Technologies/smart_open/pull/460), [chakruperitus](https://github.com/chakruperitus))
- Make our doctools submodule more robust (PR [467](https://github.com/RaRe-Technologies/smart_open/pull/467), [mpenkov](https://github.com/mpenkov))

Starting with this release, you will have to run:

pip install smart_open[gcs] to use the GCS transport.

In the future, all extra dependencies will be optional. If you want to continue installing all of them, use:

pip install smart_open[all]

See the README.rst for details.

- This is the last version to support Python 2.7. Versions 1.11 and above will support Python 3 only.
- Use only if you need Python 2.

- Various webhdfs improvements (PR [383](https://github.com/RaRe-Technologies/smart_open/pull/383), [mrk-its](https://github.com/mrk-its))
- Fixes "the connection was closed by the remote peer" error (PR [389](https://github.com/RaRe-Technologies/smart_open/pull/389), [Gapex](https://github.com/Gapex))
- allow use of S3 single part uploads (PR [400](https://github.com/RaRe-Technologies/smart_open/pull/400), [adrpar](https://github.com/adrpar))
- Add test data in package via MANIFEST.in (PR [401](https://github.com/RaRe-Technologies/smart_open/pull/401), [jayvdb](https://github.com/jayvdb))
- Google Cloud Storage (GCS) (PR [404](https://github.com/RaRe-Technologies/smart_open/pull/404), [petedannemann](https://github.com/petedannemann))
- Implement to_boto3 function for S3 I/O. (PR [405](https://github.com/RaRe-Technologies/smart_open/pull/405), [mpenkov](https://github.com/mpenkov))
- enable smart_open to operate without docstrings (PR [406](https://github.com/RaRe-Technologies/smart_open/pull/406), [mpenkov](https://github.com/mpenkov))
- Implement object_kwargs parameter (PR [411](https://github.com/RaRe-Technologies/smart_open/pull/411), [mpenkov](https://github.com/mpenkov))
- Remove dependency on old boto library (PR [413](https://github.com/RaRe-Technologies/smart_open/pull/413), [mpenkov](https://github.com/mpenkov))
- implemented efficient readline for ByteBuffer (PR [426](https://github.com/RaRe-Technologies/smart_open/pull/426), [mpenkov](https://github.com/mpenkov))
- improve buffering efficiency (PR [427](https://github.com/RaRe-Technologies/smart_open/pull/427), [mpenkov](https://github.com/mpenkov))
- fix WebHDFS read method (PR [433](https://github.com/RaRe-Technologies/smart_open/pull/433), [mpenkov](https://github.com/mpenkov))
- Make S3 uploads more robust (PR [434](https://github.com/RaRe-Technologies/smart_open/pull/434), [mpenkov](https://github.com/mpenkov))

- Add version_id transport parameter for fetching a specific S3 object version (PR [325](https://github.com/RaRe-Technologies/smart_open/pull/325), [interpolatio](https://github.com/interpolatio))
- Document passthrough use case (PR [333](https://github.com/RaRe-Technologies/smart_open/pull/333), [mpenkov](https://github.com/mpenkov))
- Support seeking over HTTP and HTTPS (PR [339](https://github.com/RaRe-Technologies/smart_open/pull/339), [interpolatio](https://github.com/interpolatio))
- Add support for rt, rt+, wt, wt+, at, at+ methods (PR [342](https://github.com/RaRe-Technologies/smart_open/pull/342), [interpolatio](https://github.com/interpolatio))
- Change VERSION to version.py (PR [349](https://github.com/RaRe-Technologies/smart_open/pull/349), [mpenkov](https://github.com/mpenkov))
- Adding howto guides (PR [355](https://github.com/RaRe-Technologies/smart_open/pull/355), [mpenkov](https://github.com/mpenkov))
- smart_open/s3: Initial implementations of str and repr (PR [359](https://github.com/RaRe-Technologies/smart_open/pull/359), [ZlatSic](https://github.com/ZlatSic))
- Support writing any bytes-like object to S3. (PR [361](https://github.com/RaRe-Technologies/smart_open/pull/361), [gilbsgilbs](https://github.com/gilbsgilbs))

- Don't use s3 bucket_head to check for bucket existence (PR [315](https://github.com/RaRe-Technologies/smart_open/pull/315), [caboteria](https://github.com/caboteria))
- Dont list buckets in s3 tests (PR [318](https://github.com/RaRe-Technologies/smart_open/pull/318), [caboteria](https://github.com/caboteria))
- Use warnings.warn instead of logger.warning (PR [321](https://github.com/RaRe-Technologies/smart_open/pull/321), [mpenkov](https://github.com/mpenkov))
- Optimize reading from S3 (PR [322](https://github.com/RaRe-Technologies/smart_open/pull/322), [mpenkov](https://github.com/mpenkov))