Update python-dateutil requirement from ~=2.7 to ~=2.8

[dependabot-preview]

Updates the requirements on python-dateutil to permit the latest version.

Changelog

Sourced from python-dateutil's changelog.

Version 2.8.0 (2019-02-04)

Data updates

• Updated tzdata version to to 2018i.

Features

• Added support for EXDATE parameters when parsing rrule strings.
  Reported by @​mlorant (gh issue #410), fixed by @​nicoe (gh pr #859).
• Added support for sub-minute time zone offsets in Python 3.6+.
  Fixed by @​cssherry (gh issue #582, pr #763)
• Switched the tzoffset, tzstr and gettz caches over to using weak
  references, so that the cache expires when no other references to the
  original tzinfo objects exist. This cache-expiry behavior is not
  guaranteed in the public interface and may change in the future. To improve
  performance in the case where transient references to the same time zones
  are repeatedly created but no strong reference is continuously held, a
  smaller "strong value" cache was also added. Weak value cache implemented by
  @​cs-cordero (gh pr #672, #801), strong cache added by
  Gökçen Nurlu (gh issue #691, gh pr #761)

Bugfixes

• Add support for ISO 8601 times with comma as the decimal separator in the
  dateutil.parser.isoparse function. (gh pr #721)
• Changed handling of T24:00 to be compliant with the standard. T24:00
  now represents midnight on the following day.
  Fixed by @​cheukting (gh issue #658, gh pr #751)
• Fixed an issue where isoparser.parse_isotime was unable to handle the
  24:00 variant representation of midnight. (gh pr #773)
• Added support for more than 6 fractional digits in isoparse.
  Reported and fixed by @​jayschwa (gh issue #786, gh pr #787).
• Added 'z' (lower case Z) as valid UTC time zone in isoparser.
  Reported by @​cjgibson (gh issue #820). Fixed by @​Cheukting (gh pr #822)
• Fixed a bug with base offset changes during DST in tzfile, and refactored
  the way base offset changes are detected. Originally reported on
  StackOverflow by @​MartinThoma. (gh issue #812, gh pr #810)
• Fixed error condition in tz.gettz when a non-ASCII timezone is passed on
  Windows in Python 2.7. (gh issue #802, pr #861)
• Improved performance and inspection properties of tzname methods.
  (gh pr #811)
• Removed unnecessary binary_type compatibility shims.
  Added by @​jdufresne (gh pr #817)

... (truncated)

Commits

• 3ebfbe8 Merge pull request #864 from pganssle/release_2.8.0
• 8e601bd Update NEWS file for version 2.8.0
• 57659e8 Move changelog for 582
• 6db5a27 Merge pull request #863 from pganssle/add_pep517
• 0519110 Add changelog for pyproject.toml changes (#863)
• 23f127f Add pyproject.toml to sdist
• c337b84 Explicitly add PEP 517 backend to pyproject.toml
• 9b9d84d Merge pull request #859 from nicoe/exdate-params
• 3997259 Add Nicolas Évrard to AUTHORS.md
• c3f4a0e Add news fragment for PR #859
• Additional commits viewable in compare view

Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting @dependabot rebase.

---

Dependabot commands and options

You can trigger Dependabot actions by commenting on this PR:

• @dependabot rebase will rebase this PR
• @dependabot recreate will recreate this PR, overwriting any edits that have been made to it
• @dependabot merge will merge this PR after your CI passes on it
• @dependabot squash and merge will squash and merge this PR after your CI passes on it
• @dependabot cancel merge will cancel a previously requested merge and block automerging
• @dependabot reopen will reopen this PR if it is closed
• @dependabot ignore this [patch|minor|major] version will close this PR and stop Dependabot creating any more for this minor/major version (unless you reopen the PR or upgrade to it). To ignore the version in this PR you can just close it
• @dependabot ignore this dependency will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself)
• @dependabot use these labels will set the current labels as the default for future PRs for this repo and language
• @dependabot use these reviewers will set the current reviewers as the default for future PRs for this repo and language
• @dependabot use these assignees will set the current assignees as the default for future PRs for this repo and language
• @dependabot use this milestone will set the current milestone as the default for future PRs for this repo and language
• @dependabot badge me will comment on this PR with code to add a "Dependabot enabled" badge to your readme

Additionally, you can set the following in your Dependabot dashboard:

• Update frequency (including time of day and day of week)
• Pull request limits (per update run and/or open at any time)
• Out-of-range updates (receive only lockfile updates, if desired)
• Security updates (receive only security updates, if desired)

Finally, you can contact us by mentioning @dependabot.

[codecov]

Codecov Report

Merging #1273 into master will not change coverage.
The diff coverage is n/a.

[dependabot-preview]

OK, I won't notify you again about this release, but will get in touch when a new version is available. If you'd rather skip all updates until the next major or minor version, let me know by commenting @dependabot ignore this major version or @dependabot ignore this minor version.

If you change your mind, just re-open this PR and I'll resolve any conflicts on it.