Add copy-to-clipboard button to meta page

Fixes #42.

assets/css/main.css

@@ -19,4 +19,12 @@ body {
 
 pre {
     padding-left: 4ex; /* approx 4 monospaced spaces */
+}
+
+.success {
+    color: #008000;
+}
+
+.fail {
+    color: #800000;
 }