Merge pull request #136 from peterdevpl/php8

PHP 8 and PHPUnit 9 support

Merge pull request #134 from xchangeapi/feature/xchangeapicom-support

xChangeApi.com support

Updated Travis config

Making Swap class not final

Merge pull request #121 from florianv/new

Updated the documentation for the new version

Fixed documentation links

Merge pull request #105 from ddinchev/master

Update swap towards latest exchanger version.

Use the latest exchanger version

Merge pull request #92 from nadsrosun/hotfix-google-finance-provider

Update to latest google finance endpoint

Merge pull request #91 from dannyweeks/add-cryptonator-service

Add Crypotonator service support