An unique keybinding for each test means we have some level of
isolation and can understand error messages more easily.
As we're >10 now, let's use a leading zero to avoid shadowed
keybindings.
The <command> arg is now optional. If omitted, :bind prints the current
binding as a message. If --mode is given, the binding for that mode is
printed.
While the original "no focused webview" bug (with the first test after spawning
qutebrowser) from #1183 was fixed, we still had a case where the next test
after ":fake-key sending key to the website with other window focused" failed,
presumably because the inspector was still focused, e.g. here:
http://qutebrowser.org:8010/builders/osx/builds/1175/steps/tests/logs/stdio
This hopefully fixes this by properly waiting until the inspector is gone.
