Upgrading PHP to 7.2 and two small fixes

[gabfr]

Q	A
Bug fix	yes
New feature	no
BC breaks	yes
Deprecations	yes
Tests pass	yes
Fixed tickets	-
License	MIT

I had to upgrade the PHP version to 7.2 because it was breaking when I used with Symfony components in v. 5. Since this may be an issue for others too and PHP 7.1 reached EOL I'm sending all the changes I did to make it happen:

• Shifted the version within the composer.json
• Changed the method signature of EightPointsGuzzleBundlePlugin::build and EightPointsGuzzleBundlePlugin::boot to match the new ones inside the symfony/http-kernel component.

I also know that perhaps this is not a so common scenario, but raising this discussion won't hurt anyone.

Thanks!

[gabfr]

This discussion was settled on the #290 PR