Add two failing header-in-codeblock tests

Both of these tests should be fixed before we can consider thlorenz#37, thlorenz#38,
and thlorenz#88 as resolved.

Credit goes to @yomed for `test/fixtures/readme-with-code.md`.

test/fixtures/readme-benign-backticks.md

@@ -0,0 +1,13 @@
+# Hello, world!
+
+> You can make code blocks with three back ticks:
+>
+> ```
+
+# Add this header
+
+<h1>And also this one</h1>
+
+> ```
+
+

test/fixtures/readme-with-code.md

@@ -0,0 +1,37 @@
+README to test doctoc with edge-case headers.
+
+<!-- START doctoc generated TOC please keep comment here to allow auto update -->
+<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
+## Table of Contents
+
+- [Single Backticks](#single-backticks)
+- [Multiple Backticks](#multiple-backticks)
+- [code tag](#code-tag)
+- [pre tag](#pre-tag)
+
+<!-- END doctoc generated TOC please keep comment here to allow auto update -->
+
+
+## Single Backticks
+`<h2>not me single backticks</h2>`
+`## nor me single backticks`
+
+## Multiple Backticks
+```
+<h2>not me fenced</h2>
+## nor me fenced
+not even me fenced
+------------------
+```
+
+## code tag
+<code><h2>not me code</h2></code>
+<code>## nor me code</code>
+
+## pre tag
+<pre>
+    <h2>not me pre</h2>
+    ## nor me pre
+    not even me pre
+    -------
+</pre>

test/transform-html.js

@@ -48,3 +48,40 @@ test('\ngiven a file that includes html with header tags using default maxHeader
   )
   t.end()
 })
+
+test('\ngiven a file with headers embedded in code', function (t) {
+  var content = require('fs').readFileSync(__dirname + '/fixtures/readme-with-code.md', 'utf8');
+  var headers = transform(content);
+
+  t.deepEqual(
+      headers.toc.split('\n')
+    , [ '## Table of Contents',
+        '',
+        '- [Single Backticks](#single-backticks)',
+        '- [Multiple Backticks](#multiple-backticks)',
+        '- [code tag](#code-tag)',
+        '- [pre tag](#pre-tag)',
+        '' ]
+    , 'generates a correct toc when headers are embedded in code blocks'
+  )
+
+  t.end()
+})
+
+test('\ngiven a file with benign backticks', function (t) {
+  var content = require('fs').readFileSync(__dirname + '/fixtures/readme-benign-backticks.md', 'utf8');
+  var headers = transform(content);
+
+  t.deepEqual(
+      headers.toc.split('\n')
+    , [ '**Table of Contents**  *generated with [DocToc](https://github.com/thlorenz/doctoc)*',
+        '',
+        '- [Hello, world!](#hello-world)',
+        '- [Add this header](#add-this-header)',
+        '- [And also this one](#and-also-this-one)',
+        '' ]
+    , 'generates a correct toc when readme has benign backticks'
+  )
+
+  t.end()
+})