Add MD014 with tests.

test/code_block_dollar.md

@@ -0,0 +1,33 @@
+The following code block shouldn't have $ before the commands:
+
+    $ ls {MD014}
+    $ less foo
+
+    $ cat bar
+
+However the following code block shows output, and $ can be used to
+distinguish between command and output:
+
+    $ ls
+    foo bar
+    $ less foo
+    Hello world
+
+    $ cat bar
+    baz
+
+The following code block uses variable names, and likewise shouldn't fire:
+
+    $foo = 'bar';
+    $baz = 'qux';
+
+The following code block doesn't have any dollar signs, and shouldn't fire:
+
+    ls foo
+    cat bar
+
+The following (fenced) code block doesn't have any content at all, and
+shouldn't fire:
+
+```
+```

test/markdownlint-test.js

@@ -31,7 +31,7 @@ function createTestForFile(file) {
     var expectedPromise = Q.nfcall(fs.readFile, file, { "encoding": "utf8" })
       .then(
         function fileContents(contents) {
-          var lines = contents.split(/\r\n|\r|\n/g);
+          var lines = contents.split(/\r\n|\r|\n/);
           var results = {};
           lines.forEach(function forLine(line, lineNum) {
             var regex = /\{(MD\d+)(?::(\d+))?\}/g;