fix bug with tag <pre>

with greedy the regular expression will match characters which should not be matched,so the tag "<pre>" must use Lazy quantifiers.

demo:

    <pre><code>npm install template-compiler -g</code></pre>

    <h2>调用</h2>

    <pre><code>atc [options] <path></code></pre>


this piece of html code can explain the bug.