Move each rule implementation into its own file (fixes #83).

lib/md006.js

@@ -0,0 +1,21 @@
+// @ts-check
+
+"use strict";
+
+var shared = require("./shared");
+
+module.exports = {
+  "names": [ "MD006", "ul-start-left" ],
+  "description":
+    "Consider starting bulleted lists at the beginning of the line",
+  "tags": [ "bullet", "ul", "indentation" ],
+  "function": function MD006(params, onError) {
+    shared.flattenLists(params).forEach(function forList(list) {
+      if (list.unordered && !list.nesting) {
+        shared.addErrorDetailIf(onError, list.open.lineNumber,
+          0, shared.indentFor(list.open), null,
+          shared.rangeFromRegExp(list.open.line, shared.listItemMarkerRe));
+      }
+    });
+  }
+};