- Documented methods and class.
- Adapted interface to the latest standard: no init list and generic container constructors, new iterator pair ctor.
- Implemented some SFINAE for managing conversions in constructors.
- Re-organised some methods to be grouped by category (modifiers, observers, iterators, ...).
- Added convenience make_span functions.
- Added some more asserts.
- Adapted test to use some syntax that was modified.