Resolve build warnings

[phoe]

The LaTeX build process at https://travis-ci.com/riichi/RiichiBooks/ emits a series of warnings, mostly about substituted fonts and unknown references. We will need to figure out which of these warnings need to be fixed and which ones, well, we can ignore.

@dainachiba Could you provide compilation logs from building the book on your own machine? We'll need to figure out if any warnings that you get also need to be fixed.

[dainachiba]

Here is a compilation log file: https://www.dropbox.com/s/j24hotlr36s1r6p/RiichiBook1.log?dl=0