Update composer.json

Update for php8 (#649)

Use Guzzle7 as default implementation (#615)

* Use Guzzle7 adapter as default implementation

Allow guzzle6 v2 adapter (#556)

Merge pull request #502 from thephpleague/v3-5.6

Allow 5.6 and 7.0

Update composer.json

Tweak composer/travis

Merge pull request #221 from dercoder/master

ecoPayz Gateway added

Bump

Bump omnipay/common requirement