gettimeofday portability

I was trying to make the code compile with visual studio 2013. This is one of the issues I ran into.
Rather than implementing a platform dependent workaround that mimics gettimeofday for windows, I replaced the code with platform independent chrono based code. 

(appologies for having 3 commits, it's the first time I created a pull request :-) 
compilation with visual studio is not working yet btw.