Computes goodness of fit for regression model given vector of target and output values.  
 
USAGE:  
   [gf] = gfit(t,y)  
   [gf] = gfit(t,y,gFitMeasure)  
       
INPUT  
t: vector of target values for regression model  
 
y: vector of output from regression model.  
 
gFitMeasure: string value representing different form of goodness of fit measure (for eg. '1' - mean squarred error, '5' - mean absolute error)  
           
OUTPUT:  
 gf: goodness of fit values between model output and target