Update syntax highlighting

Update the syntax highlighting documentation, config file, and HLJS
theme.

exampleSite/config.toml

@@ -8,7 +8,8 @@ pygmentsStyle = "trac"
 pygmentsUseClasses = true
 pygmentsCodeFences = true
 pygmentsCodefencesGuessSyntax = true
-pygmentOptions = "linenos=table"
+#pygmentsUseClassic = true
+#pygmentOptions = "linenos=inline"
 #disqusShortname = "XXX"
 #googleAnalytics = "XXX"
 
@@ -21,6 +22,7 @@ pygmentOptions = "linenos=table"
   rss = true
   comments = true
   readingTime = true
+  useHLJS = true
 #  gcse = "012345678901234567890:abcdefghijk" # Get your code from google.com/cse. Make sure to go to "Look and Feel" and change Layout to "Full Width" and Theme to "Classic"
 
 #[[Params.bigimg]]