Allow Symfony 4

[lolautruche]

Update dependencies to allow Symfony 4.

[lolautruche]

@gbtux can you please test it?

Just add dev-feat/symfony4 as version in your composer.json and run composer update.

Thanks

[Kynno]

Hi !

I just added dev-feat/symfony4 to my composer.json as the version for lolautruche/payline-bundle but it gives me the following error:

[stof]

To be compatible with a Flex project (which is likely to be the case for Symfony 4), you need to require the necessary Symfony components rather than the fullstack package. Flex is not compatible with installing symfony/symfony (that's the source of the power of auto-enabling components that get installed).
So this PR is incomplete.

Fortunately, requiring dedicated components directly also works for older Symfony versions (and that's the best practice for shared bundles since at least SF 2.7, maybe even before).