Correct ex1's ungraded exercise's testing data point

[adrianliaw]

Things modified:

• Testing data point for applying theta produced by gradient descent and normal equation. Originally the order was wrong, square-feet should go first, then number of bedrooms.
• Add feature normalization before applying the theta produced by gradient descent. As described in "Implementation Note" of section 3.1 in ex1.pdf, "We must first normalize x using the mean and standard deviation that we had previously computed from the training set."