Add page breaking and block rules to dl elements. This appears to fix #2.

The `dl` elements have been given an explicit `display:block` and page
break avoid rule. In initial testing, this fixes the wkhtmltopdf bug of
splitting lines in a multi-page document.

See http://stackoverflow.com/questions/8786755 for links and discussion.

.gitignore

@@ -1,3 +1,5 @@
 resume/_*.md
 output/*.html
 output/*.pdf
+
+resume/sample_long.md

templates/modern/css/pdf.css

@@ -89,8 +89,9 @@ body.pdf {
 
     dl {
         margin: .7em 0 0;
-        dt {
-        }
+        page-break-inside: avoid !important;
+        display: block;
+        dt {}
         dd {
         }
         strong {