The smallest REST API testing framework

The Smallest REST API testing framework in 16 lines of code (#code16challenge)

Full description and road to achieve it is described in those 2 articles (writen in Polish):

• https://testerembyc.pl/posts/20201218/najmniejszy-framework-do-testow-w-pythonie/
• https://testerembyc.pl/posts/jeszcze-mniejszy-framework-do-testow-w-pythonie/

Branches with most interesting versions of the framework:

• first article - 15 lines of code with limited functionality
• only 6 lines of code - same
  functionality as in first article, but in a limited lines of a code
• more functionality -
  code with extended testing abilities but still in 16 lines of code
• PEP-8 valid - version that is valid with PEP-8 style coding guide, functionality is somewhere in between versions with 6 lines of code and more functionality but still in 16 lines of c