Upgrade PHP version to ^7.1 and PHPUnit version to ^7

Merge pull request #19 from OpenBuildings/add-php-versions-support

Add php versions support

Update error handling

If 'paymentExecStatus' is not one of CREATED, COMPLETED, INCOMPLETE or PENDING, then the request is considered a failure and an exception is thrown. At the moment they can be "ERROR" and "REVERSALERROR"

https://developer.paypal.com/webapps/developer/docs/classic/api/adaptive-payments/Pay_API_Operation/

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Also move to scrutinizer for code coverage / analysis.

0.4.1: Fix refund request with receiver list conversion and currency

Fix refund request with receiver list converstion and currency

0.4.0: Refactor Adaptive Payments.

New class `Payment_Adaptive_Simple` is introduced as a base class for
simple, parallel and chained payments.

`Payment_Adaptive` is an abstract base class for all Adaptive Payments API calls.

`Payment_Adaptive_Refund` is introduced for the Refund API.
It extends `Payment_Adaptive` similar to `Payment_Adaptive_PaymentDetails`.

Converting receivers to receiverList is extracted into `Util::receiver_list` with
support for accountId.

Added a bit more test coverage, but new code and @covers annotations are reducing
the code coverage percent.

0.3.1

Fix merging of fields in Payment_Adaptive::do_payment

0.3.0: Make Parallel and Chained fields straightforward.

In overall the Paraller and the Chained payments should not rely on email.
Chained payments should not be responsible for selecting the primary receiver.
They should not be responsible for computing the amount for any of the receivers.
Fixes #3.
Fixes #4.

0.2.1

Make Util::parse_str() static

Overall improvements with some breaking changes in public functions

• Improve setting/getting of environment with Payment::environment()
• Introduce Util class for static helpers.
• Improve tests.
• Organize parse_response better.
• More self:: and static:: calls.
• Add PaymentDetails API operation to AdaptivePayments

0.1.2

Improve namespaces and add @covers annotations in tests

Add possibility to pass custom parameters to paypal

Merge pull request #6 from marcw/custom-parameters

Add possibility to pass custom parameters to paypal