Pull request

Couldn't wait for the docstrings, I'm nearly completed with my additions. The ``List`` instances are now able to output an EDL compatible string with their ``to_string()`` methods (also added ``Event.to_string()`` and ``Timewarp.to_string()`` etc.).

Fixed a couple of other bugs and added a couple of new methods and one new class. All my additions are done with tests prior to implementation.

Please read my commit messages. The only missing thing is the audio track information, but I'll leave it like that for a while, cause with its current form the package seems suitable to be used in our pipeline.

Edit 1:
I've also forked the ``pytimecode`` library and did a lot of fixes to it, actually I've written it nearly from scratch, and there are some conceptual changes like the ``PyTimeCode.frames`` attribute is showing the total frame count instead of the frame number and there is a new ``PyTimeCode.frame_number`` attribute for this. Also it is working much better then previous implementation, I'm waiting the owner of the ``pytimecode`` repository to accept my pull request and send the library to PyPI but if it will not happen in couple of days, I'll create a new library out of it with a new name ('pytimecode2' may be).

So, in the latest commit, I've reflected the changes in pytimecode library (frame -> frame_number other than that everything is same for python-edl).