Quoting parameter values

Please see the changes and tell me what you think about them:

In some place Python 2.6's str.format is used, so i also polished some other places:
- use decorator @staticmethod
- removed double spaces
- put two spaces before comments in the same line wit code
- exceptions raising in form Exception()
- using ternary "operator": result = True if condition else False
- if using a newer version of Python, do not load unittest2

Added space, single-quote char and other chars to the list of chars that fors parameter value to be quoted when generating icalendar content.

Before generating ical content all double quotes from parameter values are replaced with single quotes, as it is illegal to have double quotes in parameter values (https://github.com/collective/icalendar/issues/79)
Added tests