Update phpunit/phpunit requirement to ~4.4|~7.0

[dependabot-preview]

Updates the requirements on phpunit/phpunit to permit the latest version.

Changelog

Sourced from phpunit/phpunit's changelog.

Changes in PHPUnit 5.7

All notable changes of the PHPUnit 5.7 release series are documented in this file using the Keep a CHANGELOG principles.

[5.7.27] - 2018-02-01

Fixed

• Fixed #2236: Exceptions in tearDown() do not affect getStatus()
• Fixed #2950: Class extending PHPUnit\Framework\TestSuite does not extend PHPUnit\FrameworkTestCase
• Fixed #2972: PHPUnit crashes when test suite contains both .phpt files and unconventionally named tests

[5.7.26] - 2017-12-17

Fixed

• Fixed #2472: PHPUnit\Util\Getopt uses deprecated each() function
• Fixed #2833: Test class loaded during data provider execution is not discovered
• Fixed #2922: Test class is not discovered when there is a test class with [**group**](https://github.com/group) and provider throwing exception in it, tests are run with --exclude-group for that group, there is another class called later (after the class from above), and the name of that another class does not match its filename

[5.7.25] - 2017-11-14

Fixed

• Fixed #2859: Regression caused by fix for #2833

[5.7.24] - 2017-11-14

Fixed

• Fixed #2833: Test class loaded during data provider execution is not discovered

[5.7.23] - 2017-10-15

Fixed

• Fixed #2731: Empty exception message cannot be expected

[5.7.22] - 2017-09-24

Fixed

• Fixed #2769: Usage of setUseErrorHandler() produces Undefined variable error

[5.7.21] - 2017-06-21

Added

• Added PHPUnit\Framework\AssertionFailedError, PHPUnit\Framework\Test, and PHPUnit\Framework\TestSuite to the forward compatibility layer for PHPUnit 6

... (truncated)

Commits

• See full diff 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.

---

Note: This repo was added to Dependabot recently, so you'll receive a maximum of 5 PRs for your first few update runs. Once an update run creates fewer than 5 PRs we'll remove that limit.

You can always request more updates by clicking Bump now in your Dependabot dashboard.

Dependabot commands and options

You can trigger Dependabot actions by commenting on this PR:

• @dependabot rebase will rebase this PR
• @dependabot ignore this [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 yourself)
• @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 [this|these] label[s] will set the current labels as the default for future PRs for this repo and language

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

• Update frequency (including time of day and day of week)
• Automerge options (never/patch/minor, and dev/runtime dependencies)
• Out-of-range updates (receive only lockfile updates, if desired)

Finally, you can contact us by mentioning @dependabot.

[dependabot-preview]

Superseded by #4.