Switched composer package name

To comply with omnipay standards
Updated Trident gateway
Switched sale method -> purchase
Switched composer description
Added some type hinting
Moved card ID to parameter
Switched card ID to card reference
Switched invoice number -> transaction reference
Added endpoint configuration
Updated response
Added response message / error code
Updated language in readme
Fixed line endings
Merge pull request #1 from sdufel/master

Implemented gateway methods