Change default resumable chunk size to 150K.

Reviewed in http://codereview.appspot.com/5515051/
diff --git a/apiclient/http.py b/apiclient/http.py
index 6de443e..6bf1de4 100644
--- a/apiclient/http.py
+++ b/apiclient/http.py
@@ -151,7 +151,7 @@
         media_body=media).execute()
   """
 
-  def __init__(self, filename, mimetype=None, chunksize=10000, resumable=False):
+  def __init__(self, filename, mimetype=None, chunksize=150000, resumable=False):
     """Constructor.
 
     Args: