Add colon to safe characters

This matches the output from generating a SAS token using Azure portal.

Author: malthe

azure-storage-blob/azure/storage/blob/sharedaccesssignature.py

@@ -271,5 +271,5 @@ def get_token(self):
         # a conscious decision was made to exclude the timestamp in the generated token
         # this is to avoid having two snapshot ids in the query parameters when the user appends the snapshot timestamp
         exclude = [_BlobQueryStringConstants.SIGNED_TIMESTAMP]
-        return '&'.join(['{0}={1}'.format(n, url_quote(v))
+        return '&'.join(['{0}={1}'.format(n, url_quote(v, safe="/:"))
                          for n, v in self.query_dict.items() if v is not None and n not in exclude])