Fix docker-archive#7 adding support for Python 3

I have this simple update to get my script working with Python 3. 
Can anyone clarify this?

Author: arkka

dockercloud/api/http.py

@@ -34,7 +34,7 @@ def new_session():
 
 def send_request(method, path, inject_header=True, **kwargs):
     json = None
-    url = urljoin(dockercloud.rest_host.rstrip("/"), path.strip("/").encode("ascii", "ignore"))
+    url = urljoin(dockercloud.rest_host.rstrip("/"), path.strip("/"))
     if not url.endswith("/"):
         url = "%s/" % url
     user_agent = 'python-dockercloud/%s' % dockercloud.__version__