Uuid05

- added more examples in README
- unified signature of `.make()` and `.max_value()` methods
- added `--max-value` to uuid05 utility

Changed library design. Now it provides you with a class UUID05, not with bare functions.

UUID05 behaves as int, as it's a subclass of int.

It has `as_b64()` method as compact representation.

Utility now supports passing alternative characters for base64.

First release with README, tests, library and utility.