Add comments about supported anypy python versions

Help clarify which code paths will be used within the anypy shims.

Author: jerrykan

roundup/anypy/cookie_.py

@@ -1,8 +1,10 @@
 
 try:
+    # Python 3+
     from http import cookies as Cookie
     from http.cookies import CookieError, BaseCookie, SimpleCookie
     from http.cookies import _getdate as get_cookie_date
 except:
+    # Python 2.5-2.7
     from Cookie import CookieError, BaseCookie, SimpleCookie
     from Cookie import _getdate as get_cookie_date

roundup/anypy/http_.py

@@ -1,5 +1,7 @@
 try:
+    # Python 3+
     from http import client
 except:
+    # Python 2.5-2.7
     import httplib as client
 

roundup/anypy/io_.py

@@ -1,7 +1,9 @@
 
 try:
+    # Python 2.6+, 3+
     from io import StringIO, BytesIO
 except:
+    # Python 2.5
     from StringIO import StringIO
     BytesIO = StringIO
 

roundup/anypy/urllib_.py

@@ -1,6 +1,8 @@
 
 try:
+    # Python 3+
     from urllib.parse import quote, urlparse
 except:
+    # Python 2.5-2.7
     from urllib import quote
     from urlparse import urlparse