Wrap setTimeout and other async functions to allow in-flight detection.

[dalejung]

currently, if %run is run and a setTimeout is used and affects a global var, that change won't be reflected.

setTimeout( function() { global.bob = 1;}, 100);

We need a way to do the sandbox and repl globals diffing after the async stuff returns. Honestly, it's a bit like the angular digest.

Not sure if there is a global way to tell if I have an async op still in flight, maybe something in node.