fix(client.html): always open debug.html in a new browser process

Chrome reuses a single process for tabs opened by clicking links. This means that if I use debugger in debug.html it will
block the regular karma tab which will make karma think that the connection was lost.

By forcing the debug.html to be opened in a new process the original chrome tab will be unaffected while debugging with
debug.html.

Info about the rel attribute: http://blog.chromium.org/2009/12/links-that-open-in-new-processes.html