Added a simple opt loop to the example

  // Hamiltonian

  auto H = 5.907 - 2.1433 * X(0) * X(1) - 2.1433 * Y(0) * Y(1) + .21829 * Z(0) -

           6.125 * Z(1);

  const auto angles = xacc::linspace(-xacc::constants::pi, xacc::constants::pi, 20);

  for (const auto& angle: angles)

  {

    // Ansatz at a specific angle

  // TODO:

  // We can hook this up to the QCOR's Objective function

  // The amount of code to manually instantiate the optimization loop here is

  // also very minimal.

  auto optimizer = createOptimizer("nlopt");

  xacc::OptFunction f(

      [&](const std::vector<double> &x, std::vector<double> &dx) {

        const double angle = x[0];

        auto statePrep =

            std::function<void(qreg)>{[angle](qreg q) { ansatz(q, angle); }};

        double energy = 0.0;

        EstimateEnergy(q, statePrep, H, 1024, energy);

        std::cout << "Energy(" << angle << ") = " << energy << "\n";

  }

        return energy;

      },

      1);

  auto result = optimizer->optimize(f);

  std::cout << "Min Energy = " << result.first << "\n";

}