Update tzlocal

`tzlocal` version 1.1 was released, so I updated the requirements to support the newer version (`jrnl` was pinned to version 1.0).

Also, I dropped the `requirements.txt` file. Since the dependencies are noted in `setup.py` (and several are conditional), it seemed better to keep track of them in only one place. Plus, `requirements.txt` had already drifted for several dependencies...