Improve documentation around signalling

Not a bug but a suggestion:

I think it'd be easier for newbies if trickle was set to false by default. While the examples use clients on a same context and multiple candidates are shared automatically, developers will likely use a signaling server. When building out a signaling server, its not immediately obvious you need to handle multiple signals from the same peer. Setting trickle to false by default would hopefully save a lot of headaches.