style hr in the main light/dark styles, used in footnotes

Signed-off-by: Brian S. Stephan <bss@incorporeal.org>

incorporealcms/static/css/dark.css

@@ -14,6 +14,10 @@ body {
     background: #111;
 }
 
+hr {
+    color: #333;
+}
+
 h1, h2, h3, h4, h5, h6 {
     color: #B31D15;
 }

incorporealcms/static/css/light.css

@@ -14,6 +14,10 @@ body {
     background: #EEE;
 }
 
+hr {
+    color: #CCC;
+}
+
 h1, h2, h3, h4, h5, h6 {
     color: #811610;
 }