Add loading plugins in console mode (closes #286)

[rezwyi]

#286

[nolman]

I think that plugins and the console are a bit of an odd couple. People typically register things that run via an EventMachine callback (timeout/periodic timer) however with the way the console is implemented these things will not run unless you yield control back to the Reactor (Ex EM::HttpRequest).

I am hesitant about adding this because it really won't work in an intuitive way unless we fix the REPL to play well with EM.

[rezwyi]

You are right. Initialize plugins in console mode without fixed REPL is a bad idea.