First Data E4: Fix remote test.

Made it more forgiving in the process.
First Data E4: Add credential instructions

Added a comment so users of the API know what credentials they need to
use and where to find those credentials.

Figuring out the right credentials can be painful with E4 since they cut
you off for 15 minutes if you get it wrong a few times.  Hopefully these
instructions will save folks some time.

Closes #589.
Merge pull request #590 from duff/fix_e4_remote_test

First Data e4: Fix remote test
Add EVO Canada gateway

http://www.evocanada.com/

Supports credit card and check purchases, and all of EVO's API methods.

Closes #585.
Merge remote branch 'upstream/master' into finansbank_gateway