Reorganize test directory
Created by: J3FALL
Currently, in core module we have several logic submodules (composer, repository, models). However, in test directory all scripts don't organized at all. In the issue, it is planned to:
- Combine scripts in test directory according to core module hierarchy
- Make sure that pytest runs all tests correctly in Pycharm/console on Windows/Mac/etc.
- Make sure that Travis is able to successfully run tests in a cloud