Release 3.0

This is a major release that introduces the following functionality:

1. New convenience API for C++ 11 and later compilers. The library still works with C++ 98/03 compliant compilers, just without the new functions.
2. advance() function works in both directions.

The following deprecated functions were removed:

1. previous() - deprecated since version 1.02.
2. is_bom() - deprecated since version 2.3.

Thanks to the contributors:

• @glebm
• @AkiraMiyakoda
• @Al2Klimov