Fix code blocks that ignore new line
Fix missing link to social media profiles
1.  Adding intro.md to dependency list in Makefile.
2.  Switching to bullet list rather than two-column table for acknowledgments in intro.md.
1.  Putting common install instructions in a single include file `_includes/setup.html`.
2.  Modified Makefile to make `index.html` and `setup.md` depend on the new include file.
3.  Got rid of the old piecemeal setup instructions.
Removing FIXME from intro to reference guides
Fixing formatting of pipe-and-filter challenges
Switching to triple tildes for code blocks to eliminate dangling blank line
Merge branch 'fix-social-media' of github.com:r-gaia-cs/bc into fixing-social-media-links
Merge pull request #321 from gvwilson/fixing-social-media-links

Fixing social media links
Merge branch 'fix-codeblock' of github.com:r-gaia-cs/bc into fix-codeblock-in-git
Merge pull request #315 from gvwilson/fixing-intro

Re-formatting acknowledgments in intro.
Merge pull request #316 from gvwilson/refactoring-setup-instructions

Refactoring setup instructions to eliminate duplication.
Merge pull request #317 from gvwilson/removing-fixme-from-novice-ref-index

Removing FIXME from intro to reference guides
Merge pull request #318 from gvwilson/fixing-pipefilter-challenges

Fixing formatting of pipe-and-filter challenges
Merge pull request #319 from gvwilson/using-tildes-instead-of-spaces-to-indent-readme

Switching to triple tildes for code blocks to eliminate dangling blank lines in pre-formatted code