Update docs for 7.3 release

[kstefanini]

Docs is only for 7.0-beta but 7.3 is out

[ruflin]

Very good point. Recently we started to do more and more releases by just creating a release on Github and that's it. Historically I also went through the release checklist and did run the phpdocs command and published the new docs. By now, it is not just me anymore that does releases which is a great thing. But it also means we should add automation around this.

I'm challenging if the right place for docs is on Elastica.io still. Where should these phpdocs go to? Where do other libs host it?

@deguif @thePanz I'm sure you can also chime in here?

[kstefanini]

Maybe gh-pages branch could be a good place to host docs?

[ruflin]

That is where the page is already published ;-) https://github.com/ruflin/elastica/tree/gh-pages