todo list in 0.9.x

Version 0.8.5 released, main features are:
- Karatsuba multiplication
- NaN (not a number) flag in Big<> class
There will not be more features in 0.8.x branch (only bug fixes).

Now we're working on 0.9.x branch:
- support for wide characters: wchar_t, wstring, ...
- multithreading in Big<> and Parser<>
- asm for MS Visual C (x86_64)
- throwing an exception if there is a carry
- documentation (at last)
- more samples