ZeroDivisionError when calling 'MediaDownloadProgress.progress'

Resolves: #369
diff --git a/googleapiclient/http.py b/googleapiclient/http.py
index 4330f26..302e0e7 100644
--- a/googleapiclient/http.py
+++ b/googleapiclient/http.py
@@ -203,7 +203,7 @@
       the percentage complete as a float, returning 0.0 if the total size of
       the upload is unknown.
     """
-    if self.total_size is not None:
+    if self.total_size is not None and self.total_size != 0:
       return float(self.resumable_progress) / float(self.total_size)
     else:
       return 0.0
@@ -229,7 +229,7 @@
       the percentage complete as a float, returning 0.0 if the total size of
       the download is unknown.
     """
-    if self.total_size is not None:
+    if self.total_size is not None and self.total_size != 0:
       return float(self.resumable_progress) / float(self.total_size)
     else:
       return 0.0