Improved readability by correcting grammar and idioms.

Further improved language and readability.

Attempted to fix list bullets.

Again, attempted to fix list bullets.

Removed trailing whitespace on line 8.

In the camera calibration code { cv2.cornerSubPix() } will be of no use.In the updated code it is assigned to the (corners2) variable 
which is passed down to { cv2.drawChessboardCorners() }