Zero-length format string fields impact Python 2.6 support

[chrahunt]

The template strings here are not supported on Python 2.6 without indices in the {}.

[chfw]

Since python 2.6 is on its way out, python 2.6 is not planned to be supported. But I will fix it so that it can be used in python 2.6 as well.

Please be aware of this table of statues: https://devguide.python.org/#status-of-python-branches

[chfw]

the fix is released in 0.1.1.