Timecode

* **Fix:** Fixed 23.98, 29.97 DF, 29.97 NDF, 59.94 and 59.94 NDF rollover to ``00:00:00:00`` after 24 hours.

* **Fix:** Fixed a huge bug in 29.97 NDF and 59.97 NDF calculations introduced in v1.2.3.

* **Fix:** Fixed ``Timecode.framerate`` when it is given as ``23.98``. The ``framerate`` attribute will not be forced to ``24`` and it will stay ``23.98``.

* **Update:** ``Timecode.tc_to_frames()`` method now accepts Timecode instances with possibly different frame rates then the instance itself.

* **Fix:** Fixed ``Timecode.div_frames()`` method.

* **Update:** Test coverage has been increased to 100% (yay!)

* **Fix:** Fixed an edge case when two Timecodes are subtracted the resultant Timecode will always have the correct amount of frames. But it is not possible to have a Timecode with negative or zero frames as this is changed in 1.2.3.

* **Fix:** Fixed ``Timecode.float`` property for dropframe timecodes.

* **Update:** It is now possible to supply a ``Fraction`` instances for the ``framerate`` argument.

* **Update:** Passing ``frames=0`` will now raise a ValueError. This hopefully will clarify the usage of the TimeCode as a duration. If there is no duration, hence the ``frames=0``, meaning that the number of frames of the duration that this TimeCode represents is 0, which is meaningless.
* **Update:** Also added some validation for the ``frames`` property (oh yes it is a property now).

* **Update:** Version bump for PyPI.