Forwarding p5.js friendly errors, resolving #57

[ccoenen]

This defines an error message handler. This is neccessary, because the friendly error messages lead with a \n newline and thus do not get put onto the console. (apparently subsequent lines are just discarded).

It also updates p5.js to 1.4.2 and changes from minified to un-minified, because minified does not do the friendly error messages.