title: Getting "java.lang.NoClassDefFoundError: org/apache/http/nio/reactor/IOReactorException"
body: <p>I'm trying to use a Mashape api, I have added the following libraries (jars) unirest, httpasyncclient, httpclient, httpmime, org.json, commons-longging, httpcore to my project.</p>
  
  <p>I'm trying to run...</p>
  
  <pre><code>HttpResponse&lt;JsonNode&gt; response = Unirest.post("https://life-left.p.mashape.com/time-left")
  .header("X-Mashape-Key", "1NZITOdDGqmshKRAEdDbX0tp0WV2p1RR5SSjsnQYQIVwrANkhC")
  .header("Content-Type", "application/x-www-form-urlencoded")
  .field("birth", "22 April 1977")
  .field("gender", "female")
  .asJson();
  </code></pre>
  
  <p>But I get this exception...</p>
  
  <pre><code>Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/http/nio/reactor/IOReactorException
  at com.mashape.unirest.http.HttpClientHelper.prepareRequest(HttpClientHelper.java:154)
  at com.mashape.unirest.http.HttpClientHelper.request(HttpClientHelper.java:131)
  at com.mashape.unirest.request.BaseRequest.asJson(BaseRequest.java:68)
  at test.Test.main(Test.java:24)
  Caused by: java.lang.ClassNotFoundException: org.apache.http.nio.reactor.IOReactorException
  at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
  at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
  at java.security.AccessController.doPrivileged(Native Method)
  at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
  at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
  </code></pre>
  
  <p>I've tried googling around but I can't find out what is wrong.</p>
  
  <p>Any help would be appreciated.</p>