Toodledo

* You can now specify `clear=True` when creating a `TaskCache` object to clear any existing cache in the specific cache file.
* Any iterable, not just a list, can now be passed to `AddTasks` and `EditTasks`.
* The library was creating a separate OAuth2 session for every request submitted to the server. This was inefficient and unnecessary. Now only a single session is created when the `Toodledo` object is created.
* Various bugs and race conditions in `TaskCache` have been fixed, and unit tests have been added for many of them. Specifically:
* Don't barf in the cache `EditTasks` function on tasks that don't have `repeat` set.
* Fix a race condition when a repeating task is completed with `reschedule=1`.
* When `GetTasks` is called with an ID, don't nest the returned task inside an extra list.
* Fix a bug which was causing some task fields to be removed from the cache incorrectly after editing tasks.
* Fix a bug which caused the wrong tasks to sometimes be removed from the cache after editing tasks, related to what value was specified to `comp` when creating the cache.
* Make sure the date in tasks' `dueTime` field has the same date as what's in the `dueDate` field.
* The cache now always returns copies of the objects in the cache, rather than the objects themselves, so the user can't corrupt the cache by modifying the `Task` objects returned from the cache endpoints.
* To assist in debugging, primarily for debugging the library itself, there is now an internal switch which can be enabled to cause the library to save traces of recent API requests and responses.

* The TaskCache is now pass-through compatible with the Toodledo session object, meaning that all method calls available in the former are also available in the latter and vice versa, though some of them are no-ops in each object. That means that you can easily switch your code between accessing the data on the server directly and accessing it through the cache.
* The TaskCache no longer updates automatically from the server whenever you add, edit, or delete tasks. Instead, it submits your changes to the server and updates the local cache to reflect them. This significantly improves the performance of the cache. To update the cache from the server, e.g., to fetch changes made outside of your code, call the `update()` method on the cache.
* To make the API more Pythonic, the arguments to GetTasks can now be specified directly as keyword arguments, though the old syntax of putting them in the params dict is still supported for backward compatibility.
* The cache now makes an effort to emulate the behavior of the server API with regard to default values for task fields that aren't specified explicitly when it is created.

This class adds a cache for persistent local caching of tasks, so you can sync just what's changed rather than fetching all tasks repeatedly. There's more info in README.rst.

First release with Jonathan Kamens as maintainer. Lots of bug fixes and cleanup. Also code is now fully `pylint` and `flake8` clean. The README file has been augmented.