Plenty of changes, `check()` added, more unit tests added
`SwitchValueNotFoundError` renamed to `SwitchValueError`
Minor stuff
Checking multiple options at once is supported by `waspassed()`
Splitting shorts enabled by default
`undefined` type added
Started development of `NewParser()`
Implemented options adders
Started development of `Interface()` class
Refactored parser can take over old one
`isopt()` and `waspassed()` implemented in `Interface()`
basic `Interface()` finished, tests updated, manual for `NewParser()`
added
Saturday's commit
Small change in Makefile
Merge branch 'devel' of https://github.com/marekjm/clap into devel

Conflicts:
	Makefile
Ground for Formatter() prepared, unit tests written but failing
Finished initial refactoring to Formatter(), all tests pass
Support for values wrapped in apostrophes implemented in `Formatter()`
Modified tests
Code review with flake8