packaging improvements: set the "universal wheel" flag to 1, and cleaned up the setup.py. In particular removed dependency to six for setup and added py.typed file, as well as set the zip_safe flag to False. Removed tests folder from package. Fixes #1
Validate both type and value with isinstance, thanks to easy-to-write "validating types"
has_valid_type and has_valid_value methods provided for easy auditing, as well as is_vtype
Validation syntax fully compliant with valid8. Compliant error message available through a validate() method
v-types are composable so that creating a library of reusable elements is straightforward (note: should we provide one in this library based on valid8library ?)
Two styles: vtype(...) constructor method, as well as an alternate class ...(VType) style to perform composition using inheritance, and write docstrings more easily.