title: urllib3 - unable to set a http proxy
body: <p>I am trying to maintain a pool of connections to a proxy. My code looks like this:</p>
  
  <pre><code>&gt;&gt;&gt; from urllib3 import PoolManager
  &gt;&gt;&gt; pool = PoolManager(10)
  &gt;&gt;&gt; pool.urlopen('GET', 'http://http-server/index.html',fields=None,headers=None,encode_multipart=False,multipart_boundary=None,proxies={'http': 'http://proxy'})
  </code></pre>
  
  <p>When I run this, it is failing:</p>
  
  <pre><code>&gt; 
  &gt; Traceback (most recent call last):
  &gt;   File "&lt;stdin&gt;", line 1, in   &lt;module&gt;
  &gt;   File "urllib3/poolmanager.py", line 117, in urlopen
  &gt;     response = conn.urlopen(method, u.request_uri, **kw)
  &gt; File "urllib3/connectionpool.py", line 427, in urlopen
  &gt;     **response_kw)   
  &gt; File "urllib3/response.py", line 195, in from_httplib
  &gt;     **response_kw) 
  &gt; TypeError: __init__() got an unexpected keyword argument 'proxies'
  </code></pre>
  
  <p>Any idea what I am doing wrong? According to urllib3 docs, keyword args are sent to  urlopen, but looks like it is not happening in this case.</p>
  
  <p>Here is the link to <a href="http://docs.python.org/library/urllib.html#utility-functions" rel="nofollow">urllib</a> describing the usage of proxy keyword arg.</p>