title: python-markdown doesn't recognize code block?
body: <p>I'm working on a script to transfer <code>Markdown</code> to HTML, I've tried both <code>markdown</code> and <code>markdown2</code>.
  As I use <code>MathJax</code> to make it able to show math formulas in LaTex, I found <code>markdown</code> is better for me than <code>markdown2</code>.
  However, both of them don't recognize code blocks in <code>```</code>.
  My code is written in <code>Python</code>.</p>
  
  <p>My <code>Markdown</code> code is: </p>
  
  <pre><code>计算香农熵的函数：
  
  ```
  
  from math import log
  
  def calcShannonEnt(dataSet):
     numEntries = len(dataSet) #类别个数
     labelCount = {}
     for featVec in dataSet: #对每一条数据
         currentLabel = featVec[-1] #currentLabel为当前数据的类别
         if currentLabel not in labelCount.keys(): #计数
             labelCount[currentLabel] = 0
         labelCount[currentLabel] += 1
     shannonEnt = 0.0
     for key in labelCount.keys():
         prob = float(labelCount[key]) / float(numEntries)
         shannonEnt -= prob * float(log(prob,2))#计算香农熵
     return shannonEnt
  
  ```
  
  
  使用要求：
  
  - 调用的数据必须储存在列表中，且所有列表元素有相同长度
  - 列表元素的最后一列为类别
  
  [sorted函数及operator.itemgetter函数的用法详解](http://blog.csdn.net/alvine008/article/details/37757753
  </code></pre>
  
  <p>I hope those Chinese characters don't bother you.
  The HTML code is :</p>
  
  <pre><code>&lt;p&gt;计算香农熵的函数：&lt;/p&gt;
  &lt;pre&gt;&lt;code&gt;```
  
  from math import log
  
  def calcShannonEnt(dataSet):
     numEntries = len(dataSet) #类别个数
     labelCount = {}
     for featVec in dataSet: #对每一条数据
         currentLabel = featVec[-1] #currentLabel为当前数据的类别
         if currentLabel not in labelCount.keys(): #计数
             labelCount[currentLabel] = 0
         labelCount[currentLabel] += 1
     shannonEnt = 0.0
     for key in labelCount.keys():
         prob = float(labelCount[key]) / float(numEntries)
         shannonEnt -= prob * float(log(prob,2))#计算香农熵
     return shannonEnt
  
  ```
  
  
  使用要求：
  
  - 调用的数据必须储存在列表中，且所有列表元素有相同长度
  - 列表元素的最后一列为类别
  
  [sorted函数及operator.itemgetter函数的用法详解](http://blog.csdn.net/alvine008/article/details/37757753
  &lt;/code&gt;&lt;/pre&gt;
  </code></pre>
  
  <p>What's the problem?</p>