Added PHPUnit 8 support

[michalbundyra]

No description provided.

[OndraM]

I guess :void must be added as return type to tearDown() etc. methods. This is backward compatible change (won't break support for PHPUnit 7 etc.), so it could be IMHO safely done.

[michalbundyra]

@OndraM Yes, but the changes we need to do in https://github.com/php-mock/php-mock, and there we still support PHP 5.6. I can prepare compatibility level to support both versions, but not sure if it is worth to do that.

[OndraM]

Well I don't think its worth the effort: you can just drop the support of old PHP - who uses it can still use the old version of this library, it won't stop working for him. But anyone with PHPUnit 6+ must already use PHP 7+ (see https://phpunit.de/supported-versions.html ).

[KartaviK]

I agree with @OndraM . I think would be better release major version with dropped php5. In readme should point which version should use.

PS
In any case i created fork for my self :D

[michalbundyra]

I've decided to add PHPUnit 8 support without new major release.
I can't see the point of creating new major release without any additional features/changes, as adding the support of v8 was quite easy.

@KartaviK @OndraM Please have a look on PR: php-mock/php-mock#22 if you have a sec. Thanks!