Add MD032 with tests, improve infrastructure.

lib/rules.js

@@ -26,5 +26,31 @@ module.exports = {
       }
     });
     return errors;
+  },
+
+  "MD032": function MD032(lines) {
+    // Some parsers have trouble detecting lists without surrounding
+    // whitespace, so examine the lines directly.
+    var errors = [];
+    var inList = false;
+    var inCode = false;
+    var prevLine = "";
+    lines.forEach(function forLine(line, lineNum) {
+      if (!inCode) {
+        var listMarker = line.trim().match(/^([\*\+\-]|(\d+\.))\s/);
+        if (listMarker && !inList && !prevLine.match(/^($|\s)/)) {
+          errors.push(lineNum + 1);
+        } else if (!listMarker && inList && !line.match(/^($|\s)/)) {
+          errors.push(lineNum);
+        }
+        inList = listMarker;
+      }
+      if (line.trim().match(/^(```|~~~)/)) {
+        inCode = !inCode;
+        inList = false;
+      }
+      prevLine = line;
+    });
+    return errors;
   }
 };