Documentation for image.center_crop api. (#6116)
Documentation for image.center_crop api. (#6116)

* Documentation for image.center_crop api.

In order to figure out the possible interpolation techniques, I referred to http://docs.opencv.org/2.4/modules/imgproc/doc/geometric_transformations.html#void%20resize(InputArray%20src,%20OutputArray%20dst,%20Size%20dsize,%20double%20fx,%20double%20fy,%20int%20interpolation)

* Changed as per the review.

* Make the example for center_crop less verbose.

* Minor changes as per the review.

Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet