The method "decodeExceptionMessage" previous located in the
AmazonIncentives\AmazonIncentives main class has been moved to the
AmazonIncentives\Exceptions\AmazonErrors where it logically belongs.
A deprecation phpdoc message has been added for the current version.
Update error messages in curl error part and remove double spaces.
Instead of direct calling Client class and AWS class add a wrapper
method to call those so we can quicker replace under elements and
also do proper testing
Turn on mock tests on AWS side in normal test file
