ulyngs/oxforddown: Streamlined version of oxforddown

MAJOR CHANGES: The introduction chapter is now a chapter similar to all your other chapters - it should no longer be named _introduction.Rmd and is no longer a child of index.Rmd. In HTML output, the content in front-and-back-matter/_welcome-ebook.Rmd will be shown on the landing page, followed by the abstract and acknowledgements.

NEW FUNCTIONALITY:

• you can now output to the great-looking BS4 book style, with make bs4book
• for PDF output you can now
  • control the location of page numbers and running headers, as well as spacing around code blocks, directly from the YAML header in index.Rmd
  • position images and plots where they are located in the text, with the chunk option fig.pos = 'H'
  • read a new chapter with tips and tricks you need to handle tables in PDF output

MINOR CHANGES & BUG FIXES:

• the Makefile now automatically generates a docs/.nojekyll file when outputting to HTML format - this file is needed to deploy on GitHub pages
• you can now use more than one bibliography file

Enjoy!