Add hooks to generate and link PDF files.
Add link to PDF files in documentation site.
Add necessary packages to Travis/README for pdf generation.
Alter PDF generation to be language aware.

* Detect langauge by directory name
* Allow different pandoc arguments by language.
* Add --toc argument.
Lots of PDF fixes.

* Create header-content before generating PDF.
* Pull title from first H1 in the doc.
* Customize latex arguments per-language (correctly)
* Fix passing arugments to latex
* Add debugging output of pandoc calls.
Fail on pdf error and add more texlive to travis.
Add texlive backport PPA to make travis build correctly.
Fix the do you want to install prompt
Merge pull request #7 from sbt/wip/make-pdf

Generate + Link PDF documents in the documentation.