Switch the markdown engine to kramdown as GitHub are getting rid of redcarpet :( (#201)

* Remove errant .DS_Store file

* Ignore .DS_Store

* Create a list of organisations

* Add an org list

* Show number of PIDs per org

* Fix HTML issue, sort orgs by title

* Try and fix the PID count

* Try and fix issues

* Try again to fix issues

* Try yet again to fix issues

* Correct the urlpart

* Change to sort_natural, minor code tidy

* Try and fix the sorting

* Try again to fix the sorting

* Remove debugging

* Add a link to orgs page

* Turn on the remaining redcarpet extensions so we match GitHub

From https://george-hawkins.github.io/basic-gfm-jekyll/redcarpet-extensions.html

* Switch to kramdown

* Turn on some other options

Author: peternewman

_config.yml

@@ -47,10 +47,13 @@ share_stumbleupon: false
 exclude: [vendor]
 gems:
  - jekyll-paginate
- - redcarpet
-markdown:     redcarpet
-redcarpet:
-  extensions: ['smart', 'tables', 'with_toc_data']
+markdown:     kramdown
+kramdown:
+  auto_ids: true
+  autolink: true
+  input: GFM
+  toc_levels: 1..6
+  smart_quotes: lsquo,rsquo,ldquo,rdquo
 permalink:    pretty
 paginate:     3
 sass: