upip: Use new JSON API pointing to pypi.org.

So upip doesn't have to follow redirects.

upip/upip.py

@@ -156,7 +156,7 @@ def url_open(url):
 
 
 def get_pkg_metadata(name):
-    f = url_open("https://pypi.python.org/pypi/%s/json" % name)
+    f = url_open("https://pypi.org/pypi/%s/json" % name)
     try:
         return json.load(f)
     finally: