Add continuous integration

[phoe]

The problems at #5 currently make me think that it is non-trivial to build Riichi Book on one's own - for instance, piemf fonts need to be downloaded and installed manually, I encountered encoding issues that prevented some Japanese text in piemf TeX files from compiling, and the fonts that I had installed (I had texlive-full installed on Ubuntu) did not fully match the ones in the PDF.

My suggestion is to have GitHub's continuous integration, Travis, try and build the PDF automatically on each commit or pull request to the repository. That will make it unnecessary to manually build and upload the book on each text change, make it possible easier for other people to build the book from scratch, and will check that all commits result in valid and buildable TeX code.

I will try to do this on a fork of this repository, as soon as I figure out the steps to build the book myself at #5. Then I will try to reproduce these steps on a clean Linux installation, which will in turn make it possible to tell Travis how to build it.

[dainachiba]

Thank you for the suggestion. I had never heard of Travis before, but it sounds interesting and promising. Please let me know what you find out.

[phoe]

Some progress: Travis successfully builds the book, as seen at https://travis-ci.com/riichi/RiichiBooks/jobs/241027935

The current goals are:

• tell Travis to upload the resulting PDF file to GitHub releases of the repository
• strip the installed dependencies, since we likely do not need the full texlive-full package installed to build the book - this will speed up builds.

[phoe]

Travis has been configured on our fork and the most fresh release is pushed into https://github.com/riichi/RiichiBooks/releases

Example run: https://travis-ci.com/riichi/RiichiBooks/jobs/241080592

As soon as we figure out some issues with image setting in the resulting PDF file, we will prepare a PR to this repository.