Make spaces visible using CSS.

Closes #49.

I didn't want to actually insert the characters, since I want
the code samples to be cut/pasteable.  But this CSS trick seems
to work.

Makefile

@@ -37,9 +37,10 @@ spec.md: $(SPEC)
 
 spec.html: spec.md template.html
 	pandoc --no-highlight --number-sections --template template.html -s --toc -S $< | \
-	perl -pe 's/a href="@([^"]*)"/a id="\1" href="#\1" class="definition"/g' > $@
+	perl -pe 's/a href="@([^"]*)"/a id="\1" href="#\1" class="definition"/g' | \
+	perl -pe 's/␣/<span class="space"> <\/span>/g' \
+	> $@
 
-	 # | perl -pe 's/␣/<span class="space"> <\/span>/g' > $@
 
 spec.pdf: spec.md template.tex specfilter.hs
 	pandoc -s $< --template template.tex \

spec2md.pl

@@ -29,7 +29,7 @@ while (<STDIN>) {
         $section = $match[0];
     }
     if ($stage != 0) {
-      #  $_ =~ s/ /␣/g;
+      $_ =~ s/ /␣/g;
     }
     print $_;
   }