moved usb-specific code down to the device plugins that actually use it
Maybe we want to fully initialize the driver class instead, then yield that?
Refactor #38; Fix formatting
Update tutorial.rst

Add djvulibre-bin dependency for djvubind to list of packages to be apt-get installed.
Merge pull request #41 from markvdb/patch-2

docs: Add djvulibre-bin dependency for djvubind to package list in tutorial