Remove peerjs dependency

[hugooliveirad]

Using peerjs by default is not a good thing. I chose to use it as I didn't want to implement a server from scratch due to time constraints before the first delivery of this app.

Now, there's no need to continue using it and the users would benefit from having a more flexible and open way to connect between their peers.

So, there are three things I'd like to do:

• Make offline version the default.
• Provide optional default server.
• Enable users to set their own servers to be used by peerdocs.

An optional stretch would be to:

• Provide interface so that users can plug their scripts and define how the communication with the world is done, under their terms. I'm not entirely sure how that would work though. It would probably be easier to just let the users change some build configs or even the source code directly and support this option somehow.