Update README and rockspec for 1.0.0

The README documents unpack returning the position, size, the new options, how numbers are handled and what differs from the C library.
It lists the changes which can affect code written for 0.9.
The rockspec uses git+https because GitHub turned the git:// protocol off in 2022.

Merge pull request #19 from zhucebuliaopx/master

fix pr#17 && unit test && add Travis CI

Include c0 in README

Remove publish