Maxwell Boltzmann Initial Distribution

[jakehanson]

Add a flag so that particles can start with a maxwell boltzmann distribution with temperature T.

[jakehanson]

Proposed API

void Ants::populate(double L, double H, double T,double r_enc,int max_init, int seed)
{
	std::mt19937 gen(seed); // create generator with default seed
	std::normal_distribution<double> nd(0.,1.0); // init normal dist with mean 0 and stddev 1
	std::uniform_real_distribution<double> uni(0.,1);

...

	x_velocities.at(i) = sqrt(T)*nd(gen);
	y_velocities.at(i) = sqrt(T)*nd(gen);
}