Test environment and some refactoring.

- Update README.md
- "punch in/out" seems is most widely used than "clock in/out"
- Specify versions for some gems and change RSpec for Minitest.
- Set up test simple test environment with Minitest.
- Secret option provided to Rack::Session::Cookie.
- Fix ambiguos expression in conditional (change = by ==).
- Add Modules and wraps some dependencies in our own classes.
- Add tests for the OmniAuth wrapper.
- Add first models.
- Replace explicit queries by models.
- Set up Minitest with Guard and reorganize the test structure.
- Add migrations to create the partioned schema for registers.
- Move the logic of tolerating uniqueness errors to the model. (But it is still a smell)
- Tyding up test structure (again).
- Change the name of the table to match the model name.
- Some refactoring and shorten code.