Just ignore all tarballs
Rename the library to libcangjie

I asked Wan Leung, and he agreed to letting us reuse the name
"libcangjie" instead of "libcangjie2".

This should make life easier for packagers in Linux distributions, as
they can just upgrade their packages instead of having to create new
ones, make them obsolete the old one, play the bureaucracy games of
retiring the old package, etc...

All in all, it just makes more sense, as this is really the follower of
Wan Leung's original library, even though it's a complete rewrite.

We are very grateful to Wan Leung for letting us reuse the name.
Rephrase some comments a bit

Now that we are also called "libcangjie", some references to Wan Leung's
original library did not make a lot of sense any more.

This should make them clearer.