Add basic infrastructure, MD031, and test.

lib/markdownlint.js

@@ -0,0 +1,27 @@
+"use strict";
+
+var fs = require("fs");
+var rules = require("./rules");
+
+function lintFile(file, options) {
+  var results = {};
+  var contents = fs.readFileSync(file, { encoding: "utf8" });
+  var lines = contents.split(/\r\n|\n/g);
+  Object.keys(rules).forEach(function(name) {
+    var rule = rules[name];
+    var errors = rule(lines);
+    if (errors.length) {
+      results[name] = errors;
+    }
+  });
+  return results;
+}
+
+module.exports = function(options) {
+  var results = {};
+  var files = options.files || [];
+  files.forEach(function(file) {
+    results[file] = lintFile(file, options);
+  });
+  return results;
+};