Observers Doc refers to missing template

[jnphilipp]

The section Template Rendering refers to sacred/examples/my_runs/template.html which no longer exists.

[thequilo]

Yes, that's right. You can create a pull request if you like.

While looking at the code, I realized that there is a bug in the template rendering: If you provide a template file but mako is not installed, the code just runs through but doesn't create a rendered file. It also looks like the rendering code expects a pathlib.Path but the argument is never converted or checked.