Simulation mode for experiments

[nikbpetrov]

Hi everyone!

Hope this is the right place! I've been working on creating a simulation mode for experiments that would allow you to automatically run through your experiment, simulate a real participant and save the data (addressing #647 ).

I've put together such an implementation with this pull request (#1886 ). In essence, it creates a simulate method for all available plugins which mimics the behaviour of a real participant. Running simulation mode is as easy as adding simulate: true to your jsPsych.init method -- and there is also tons of customization you can implement during the simulation mode!

Any and all feedback is welcome!