Initial import of updated PHP Library-- pending review.
Adding PHP Formatting.
Separated Data / Object classes & using AutoLoader.
Cleaned up formatting & adding path specifications.
Changed errors to be exceptions instead of echos.
Adding base framework for unit testing.
Adjusting structure for test classes.
Revert "Adjusting structure for test classes."

This reverts commit a2777a362a9a6fbbee766b583db11bfe3c576c8f.
Restructured classes to use namespaces and SplClassLoader.
Adjusted namespace to be all caps.
Adjusted errors w/ namespace.
Removing unused file.
Adjusting error messages / exception handling.
Updated readme, updated min PHP version, and added necessary constant.
Fixed error messages & exception throwing in receipts.
Updated CreditCardStorage example.
Fixed Recurring Purchase example.
Fixing typos.
Added single purchase example.
Updated Readme.