Adds a simple stopwatch class that allows similar functionality to MATLAB's tic toc commands.
#include "stopwatch.hpp"
[...]
stopwatch s;
s.tic();
[code to be timed here]
s.toc();
std::cout << "Elapsed time: " << s << " seconds." << std::endl;
std::cout << "Half of elapsed time: << s.elapsed() / 2.0 << " seconds." << std::endl;