- `num` dependency is gone. It was only used for floored division
and it is not hard to copy only that portion from num.
- `Duration + Date` (or so) was blocked by rust-lang/rust#7590,
which has been subsequently fixed.
- Removed unused `unsafe` checks.
- `std::fmt::WriteError` is now `std::fmt::Error`.
- abandoned rust-ci for documentations (sorry, but it didn't work
nowdays ;_;), we are now publishing directly to Github pages.
Kang Seonghoon