Improved namespace structure.

[janhryniukpgs]

Issue #, if available:

Description of changes:

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[biplobice]

Using AmazonPayTest and changing the directory name from tst to test could be a better choice.

[janhryniukpgs]

Hi.
After making suggested changes this conflicts appears.
It would be nice if someone will check settings of repository and tell me, why this conflict appear.

[nlubisch]

@janhryniukpgs The conflict appears because during your change the ClientTest has been updated.
See aff849d

Your have to rebase your branch onto master, fix the conflicts and force push.

[janhryniukpgs]

Done.