Would it be possible to add a configurable way to select Bootswatch version?

[shichao-an]

It seems the latest version of sphinx-bootstrap-theme (0.4.0) that uses Bootswatch 3.1.0 breaks my original layout. I didn't figure out a way to configure it to choose Bootwatch 3.0.0, so I had to revert sphinx-bootstrap-theme back to 0.3.6 that uses Bootswatch 3.0.0.

[ryan-roemer]

The existing bootswatch files we use have a large footprint already, so we can't just include all versions. One potential extension would be to leave open a "custom bootswatch" option that permits and arbitary css link to be used, which the user could then upload to their own _static directory in their Sphinx source...