Numbered release

[Sam-Burns]

I suggest we do a new numbered release sometime soon, along with the changes to the language version requirements.
@svpernova09 have you got admin access to the Packagist package btw?

Perhaps it would be a good idea to introduce some PHP7 typehinting, before we do that. It would be a BC breaking change, but we could release the library at version 1.0.0 after this and any other pending changes.

Thoughts?

[svpernova09]

So we're already tagged with the recent changes I did last week-ish https://github.com/PiPHP/GPIO/releases/tag/0.2.2

I went with https://0ver.org/ over traditional semantic versioning since the only previous releases were development.

[svpernova09]

And looking at tags, there are several tags that didn't have GH releases attached to it. So we may need to bump up to 0.4.x to get past them.

[svpernova09]

I'm about to tag 0.4.0 against master. This pulls our version higher than previously tagged versions. I missed the fact we have tagged versions that aren't GH releases so my starting versioning was too low.