title: Undefined symbol using charlock_holmes gem
body: <p>I installed icu on amazon ec2 with </p>
  
  <pre><code>sudo apt-get install libicu-dev
  </code></pre>
  
  <p>Then I installed charlock_holmes: </p>
  
  <pre><code>gem install charlock_holmes
  </code></pre>
  
  <p>It seemed to me that it was successfully installed: </p>
  
  <pre><code>Building native extensions. This could take a while...
  Successfully installed charlock_holmes-0.6.9.4
  1 gem installed
  </code></pre>
  
  <p>After that I got this:</p>
  
  <pre><code>.../shared/bundle/ruby/1.9.1/gems/charlock_holmes-0.6.9.4/lib/charlock_holmes.rb:1:in `require':
  .../shared/bundle/ruby/1.9.1/gems/charlock_holmes-0.6.9.4/lib/charlock_holmes/charlock_holmes.so: 
    undefined symbol: _ZN6icu_518ByteSink15GetAppendBufferEiiPciPi   
  .../shared/bundle/ruby/1.9.1/gems/charlock_holmes-0.6.9.4/lib/charlock_holmes/charlock_holmes.so (LoadError)
  </code></pre>
  
  <p>I tried also to install using this command:</p>
  
  <pre><code>gem install charlock_holmes -- --with-icu-dir=/usr/local/lib/
  </code></pre>
  
  <p>The error still occures.
  It seems to me that somehow I need to specify the right directory <code>--with-icu-dir</code></p>
  
  <p>The reason why I specified <code>/usr/local/lib</code> is because the icu libs are installed into that directory.</p>