Fix margins and kerning in listings area.

preamble.tex

@@ -81,7 +81,7 b''
   extendedchars=\true,
   aboveskip=\smallskipamount,
   belowskip=\smallskipamount,
-  %xleftmargin=3mm,
+  xleftmargin=2mm,
   breaklines=true,
   basicstyle=\small \ttfamily,
   showstringspaces=false,
@@ -89,6 +89,7 b''
   commentstyle=\color{myteal},
   stringstyle=\color{darkgreen},
   identifierstyle=\color{darkorange},
+  columns=fullflexible,  % tighter character kerning, like verb
 }
 
 % The hyperref package gives us a pdf with properly built