* `then()` is deprecated, just use strings and `+`, like `'C-' + exactly(8, digits)` or `one_or_more(digits) + '°'`.
* `groups()` and `group()` are methods with same semantics as `re`'s.
* Added `hex`, `hexa` that matches hexadecimal digits.
* Support broken day representations like in `Apr 7 07:46:44` (it should be `07`).