Add notifyUrl tests
Fix tests
Add notifyUrl and issuer fields to example app
Add Mollie gateway
PSR2 style fixes
Update README.md
Remove debug comment
Pass amount as decimal instead of integer
Add CHANGELOG.md
Update README.md
Update CHANGELOG.md
Update README.md
Style fix
Update README.md
Add Buckaroo gateway
Style fix
Fix concatenation typo
Merge pull request #77 from winzou/patch-1

Fix concatenation typo
Step into the future
Require guzzle/http 3.1+