Replaced named attributes with absolute indices in order to work on wide range of Python versions.

According to python documentation, named attributes were not added to sys.version_info until 3.1. http://docs.python.org/3/library/sys.html#module-sys 

2.6 was correctly failing, but not because of the version test, but due to AttributeError trying to access the sys.version_info.major and sys.version_info.minor named attributes.

Replaced named attributes with absolute indices in order to work on wide range of Python versions.