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

lib/md019.js

@@ -0,0 +1,21 @@
+// @ts-check
+
+"use strict";
+
+var shared = require("./shared");
+
+module.exports = {
+  "names": [ "MD019", "no-multiple-space-atx" ],
+  "description": "Multiple spaces after hash on atx style header",
+  "tags": [ "headers", "atx", "spaces" ],
+  "function": function MD019(params, onError) {
+    shared.filterTokens(params, "heading_open", function forToken(token) {
+      if ((shared.headingStyleFor(token) === "atx") &&
+          /^#+\s\s/.test(token.line)) {
+        shared.addErrorContext(onError, token.lineNumber, token.line.trim(),
+          null, null,
+          shared.rangeFromRegExp(token.line, shared.atxHeaderSpaceRe));
+      }
+    });
+  }
+};