Plugin doesn't work well through reverse proxy

[derekantrican]

I have my octoprint set up through a reverse proxy, so I connect to it via http://mydomain.com/octoprint. I've noticed some things don't work properly. Just a preliminary list I found:

• The "Test sensor" button doesn't work as it throws a 404 error (I had to modify the filamentsensorsimplified.js to figure that out - might want to add some more logging)
• The logo in the bottom right of the settings pane doesn't load (see below)

And there may be more things. It may not be necessary to change them, but I think it'd at least be helpful to add something in the readme or elsewhere that some features might not work properly.

[derekantrican]

The logo issue could be solved if you linked to a website (eg https://d1fdloi71mui9q.cloudfront.net/AXlRNgdJQQq8z6dy3ifY_p22OLMq4k3QgR59n ) rather than a relative link to the plugin