Update isort to 4.3.4

[pyup-bot]

This PR updates isort from 4.2.15 to 4.3.4.

Changelog

4.3.4

- Fixed issue 671: isort is corrupting CRLF files

4.3.3

- Fixed issue 665: Tabs turned into single spaces

4.3.2

- Fixed issue 651: Add imports option is broken
- Fixed issue 662: An error generated by rewriting `.imports` to `. imoprts`

4.3.1

- Fixed setup.py errors
- Fixed issue 654: Trailing comma count error
- Fixed issue 650: Wrong error message displayed

4.3.0

- Fixed 557: `force_alphabetical_sort` and `force_sort_within_sections` can now be utilized together without extra new lines
- Fix case-sensitive path existence check in Mac OS X
- Added `--no-lines-before` for more granular control over section output
- Fixed 493: Unwanted conversion to Windows line endings
- Fixed 590: Import `as` mucks with alphabetical sorting
- Implemented `--version-number` to retrieve just the version number without the isort logo
- Breaking changes
 - Python 2.7+ only (dropped 2.6) allowing various code simplifications and improvements.

Links

• PyPI: https://pypi.org/project/isort
• Changelog: https://pyup.io/changelogs/isort/
• Repo: https://github.com/timothycrosley/isort