Changes:
* The ``load_dataset`` task now accepts a ``bulk_mode`` option which can be set to ``Serial`` to load batches serially instead of in parallel.
* CumulusCI now stores the logs from the last five executions under ``~/.cumulusci/logs``
* CumulusCI has a new top-level command: ``cci gist``. This command creates a secret GitHub gist which includes: The user's current CumulusCI version, current Python version, path to python binary, sysname (e.g. Darwin), machine (e.g. x86_64), and the most recent CumulusCI logfile (``~/.cumulusci/logs/cci.log``). The command outputs a link to the created gist and opens a browser tab with the new GitHub gist. This can be helpful for sharing information regarding errors and issues encountered when working with cci. This feature uses a users GitHub access token for creation of gists. If your access token does not have the 'gist (Create gists)' scope this command will result in a 404 error. For more info see: https://cumulusci.readthedocs.io/en/latest/features.html#reporting-error-logs
* Changed ``UpdateAdminProfile`` so that it only deploys the modified Admin profile. While it is necessary to retrieve profiles along their associated metadata objects, we don't need to do that for deployments.
* Added options to the `deploy` task: ``check_only``, ``test_level``, and ``specified_tests``. Run ``cci task info deploy`` for details. (1066)