Adding ssl_version parameter to Urllib3HttpConnection

Fixes #246

elasticsearch/connection/http_urllib3.py

@@ -20,12 +20,15 @@ class Urllib3HttpConnection(Connection):
         for instructions how to get default set
     :arg client_cert: path to the file containing the private key and the
         certificate
+    :arg ssl_version: version of the SSL protocol to use. Choices are:
+        SSLv23 (default) SSLv2 SSLv3 TLSv1 (see ``PROTOCOL_*`` constants in the
+        ``ssl`` module for exact options for your environment).
     :arg maxsize: the maximum number of connections which will be kept open to
         this host.
     """
     def __init__(self, host='localhost', port=9200, http_auth=None,
             use_ssl=False, verify_certs=False, ca_certs=None, client_cert=None,
-            maxsize=10, **kwargs):
+            ssl_version=None, maxsize=10, **kwargs):
 
         super(Urllib3HttpConnection, self).__init__(host=host, port=port, **kwargs)
         self.headers = urllib3.make_headers(keep_alive=True)
@@ -38,6 +41,7 @@ class Urllib3HttpConnection(Connection):
         kw = {}
         if use_ssl:
             pool_class = urllib3.HTTPSConnectionPool
+            kw['ssl_version'] = ssl_version
 
             if verify_certs:
                 kw['cert_reqs'] = 'CERT_REQUIRED'