ENH: Build PDF documentation

[larsoner]

From @mkajola in #29 (comment) :

Do we have the Manual somewhere in github, or only the tag directory text file

Only the text files. I don't know how you all build the manual, but if you can share the LaTeX structure to do it I can make a CI system (probably CircleCI) rebulid the doc on every pull request / merge / tag. That way we can look at the newest doc whenever we want, and when we make a release we could include it for example.