Send placeholder message to clients when last host is closed
Add a boot route, redirects to the home page with a flash message.
Make bootClient message actually boot out the client.
Ensure noisebox is destroyed when last host leaves.
Prevent user page from being cached.

This fixes a problem where the user page was able to be displayed even after all the hosts had gone.
Merge pull request #71 from GuntLondon/m-allanson/49-killing-a-host

m-allanson/49 killing a host