Merge pull request #553 from tombell/vthree-rethink

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robot extends eventemitter

this is more idiomatic for node applications
Merge pull request #559 from tombell/vthree-rethink-robot-eventemitter

robot extends eventemitter
add uncaught exception event handler
add error handlers array and event listeners

the array of error handler functions are looped over and invoked with the
uncaught exception or user trigger error event error.
add function for adding error handlers