Make pyScss compatible again with python 2.5.

The change introduced in changeset 4da61e4 broke the compilation of scss files with Python 2.5 : the parameter 'break_on_hyphens' of  textwrap.TextWrapper() constructor has been added in Python 2.6.

However, the readme claims as requirement "python >= 2.5".

Another solution would be to remove completely support for python 2.5.

*On a sidenote*: I maintain (when I have some time) to maintain the extension Flask-Scss that uses pyScss as its compilation engine, and as Flask supports python 2.5, I am required to support it too, which motivates this request.