Do a better job preserving nodeunit's 'this', and fix setTimeout ret values

Hello @x-ma, 

Please review the following commits I made in branch 'nick-thisobj'.

190827668d07dfbcdde2c94fb0ab18874d9f612b (2014-01-22 18:07:12 -0500)
Do a better job preserving nodeunit's 'this', and fix setTimeout ret values

R=@x-ma