revises tocbot configuration and documentation

layouts/partials/page-single/footer.html

@@ -4,3 +4,21 @@
 {{ end }}
 {{ partial "footer/font-awesome-js.html" . }}
 {{ partial "highlight-js.html" . }}
+{{ with .Site.Params.toc }}
+{{ if eq . "tocbot" }}
+<script src="https://cdnjs.cloudflare.com/ajax/libs/tocbot/4.1.1/tocbot.js"></script>
+<script type="text/javascript">
+  if (tocbot) {
+    tocbot.init({
+      // Where to render the table of contents.
+      tocSelector: '.toc',
+      // Where to grab the headings to build the table of contents.
+      contentSelector: '.post',
+      // Which headings to grab inside of the contentSelector element.
+      headingSelector: 'h2, h3, h4',
+      collapseDepth: 4
+    });
+  }
+</script>
+{{ end }}
+{{ end }}