Replace Word-generated PDF with Markdown source code

Markdown may be converted to HTML or PDF for sharing using Pandoc:

    pandoc -s -o "Introduction to PHP.html" "Introduction to PHP.md"

    pandoc -s -o "Introduction to PHP.pdf" "Introduction to PHP.md"

Converting to PDF also requires a version fo LaTeX. See the Pandoc
documentation for details.

    http://johnmacfarlane.net/pandoc/README.html
Fix up spacing from conversion to Markdown
Convert README to Markdown
Fix paragraph breaks based on original PDF
Add inline code styling as per original PDF
Merge branch 'markdown'
Use Pandoc title block and add title image
Add inline code delimiters
Add PDF building instructions to README.md
Add PDF and HTML files to .gitignore
Replace “smart quotes” with "regular quotes"

Via LaTeX, Pandoc will fancy these up in text when building PDFs, but
will leave proper straight quotes in source code.