Icalendar

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- Update Release information.
[thet]

---

- Add API for proper Timezone support. Allow creating ical DATE-TIME strings
with timezone information from Python datetimes with pytz based timezone
information and vice versa.
[thet]

- Unify API to only use to_ical and from_ical and remove string casting as a
requirement for Python 3 compatibility:
New: to_ical.
Old: ical, string, as_string and string casting via __str__ and str.
New: from_ical.
Old: from_string.
[thet]

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- migration to https://github.com/collective/icalendar using svn2git preserving
tags, branches and authors.
[garbas]

- using tox for testing on python 2.4, 2.5, 2.6, 2.6.
[garbas]

- fixed tests so they pass also under python 2.7.
[garbas]

- running tests on https://jenkins.plone.org/job/icalendar (only 2.6 for now)
with some other metrics (pylint, clonedigger, coverage).
[garbas]

- review and merge changes from https://github.com/cozi/icalendar fork.
[garbas]

- created sphinx documentation and started documenting development and goals.
[garbas]

- hook out github repository to https://readthedocs.org service so sphinx
documentation is generated on each commit (for master). Documentation can be
visible on: https://icalendar.readthedocs.io/en/latest/
[garbas]

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- Fix deprecation warnings about ``object.__init__`` taking no parameters.

- Set the VALUE parameter correctly for date values.

- Long binary data would be base64 encoded with newlines, which made the
iCalendar files incorrect. (This still needs testing).

- Correctly handle content lines which include newlines.

------------------

- Made the tests run under Python 2.5+

- Renamed the UTC class to Utc, so it would not clash with the UTC object,
since that rendered the UTC object unpicklable.

----------------

- EXDATE and RDATE now returns a vDDDLists object, which contains a list
of vDDDTypes objects. This is do that EXDATE and RDATE can contain
lists of dates, as per RFC.

***Note!***: This change is incompatible with earlier behavior, so if you
handle EXDATE and RDATE you will need to update your code.

- When createing a vDuration of -5 hours (which in itself is nonsensical),
the ical output of that was -P1DT19H, which is correct, but ugly. Now
it's '-PT5H', which is prettier.