Request to remove Voyager

[kernelpanek]

Voyager was awesome for a time when Jupyterlab was in its version 1.0 days, but the Voyager project has not kept up with dependencies. Voyager no longer works for Jupyterlab v2 or v3 and I would recommend that it no longer be considered to be "awesome." If full removal isn't satisfactory, then I recommend that the readme document be updated to note that the extension no longer works with current versions of Jupyterlab.