singleton takes args and kwargs (#10)

pass correct message to QPayException (#9)

Merge pull request #7 from khasbilegt/production-invoice-logo-and-sho…

…rt-url

qpay invoice bank logo and short url

Merge pull request #6 from khasbilegt/update-payment-related-methods

Update payment related methods

Merge pull request #3 from khasbilegt/change-package-name

change package name