Refactor the code so it is more testable:

- Add dependency injection to the payflow class.
- Add more tests.
- Make payflow class test independend from http using mock object.
Perform setup tasks:

- Make PayFlow class test public.
- Instruct Travis to install dev version of the package.
Decouple gateway configuration
Combine payflow configuration into one array
Add additional parameters to the PayFlow gateway
Add static variable declaration that will hold child object
Change filter invocation method
Add AuthorizeAIM gateway
Rename Authorize gateway
Update servlet set method and add one more param
Pass servlets to the Gateway abstract class from gateway implementation class
Remove Signature param from PayFlow gateway
Start with PayPal gateway
Continue with Paypal gateway
Clean up the code
Bring some addjustments from master
Make x_email_customer param not defautl and common so it can be set before the method call
Add new method to Silverpop API
Merge branch 'refactor'

Conflicts:
	SankyNet/API/PayFlow.php