Incorporate `Jupyter.notebook.base_url` when fetching the MarkUs API key file.
0.1.3
Enable API key to be stored in the user home directory on JupyterHub. Improve user messages.
0.1.2
Enable [automatic installation](https://jupyter-notebook.readthedocs.io/en/stable/examples/Notebook/Distributing%20Jupyter%20Extensions%20as%20Python%20Packages.html#Automatically-enabling-a-server-extension-and-nbextension) of extension.
0.1.1
Initial release of [markus-jupyter-extension](https://github.com/MarkUsProject/markus-jupyter-extension/).