Introduction - If you have any usage issues, please Google them yourself
		 
 This function calculates the POD basis vectors 
 
 Function inputs:
 X : (n x nsnap) snapshot matrix
 n = number of states in full space
 nsnap = number of snapshots
 cenergy : how much energy of the ensemble you want 
 to capture, i.e. cenergy = 99.9 (percent)
 
 Function outputs:
 phi : (n x nsnap) matrix containing POD basis vectors
 lam : (nsnap x 1) vector containing POD eigenvalues
 Xmean : (n x 1) the mean of the ensemble X
 nbasis : number of POD basis vectors you should use
 to capture cenergy (percent) of the ensemble