Add Chinese translation plus new travis.yml

[onionhoney]

• Started work on the Chinese translation of the book. (about 50% done)
• Updated book.toml and file structure per requirement of the multilingual fork
• Of course I got travis CI working as well.

While mdbook doesn't have official support for multilingual, this awesome fork is used instead (see original discussion here). To run it locally you'll have to compile it yourself with cargo build.