Add testcases for baseline testing app

[gribok]

Let's add some testcases for unittesting of help function, like date.is_date and integration testcases for api endpoints, like /deaths.

I will try to provide a testsuite for testing of baseline to avoid breaking changes.

Next step could be to setup a Travis CI chain for auto-checking of every PR.
Let me know, if I can help.

[ExpDev07]

I will be pushing /v2/ soon which introduces new core code and features. Once that's good I'd love your help to start implementing test cases 👍

[gribok]

Pushed my changes via PR. Check it out and let me know. 👍

[gribok]

I am gonna to close the issue. Testsuite introduced.