Suggestion: add an example that uses ImageRecordIterator with RGB images

[pasondag]

Hi Soonhwan,

Thanks for creating this repo. This first implementation of CapsNet in MxNet is quite useful. It is great to be able to (almost) reproduce the performances of the paper on MNIST. To be more generally useful, a great addition to your repo would be to add an example using the ImageRecordIterator on RGB images which is what is generally used / needed.

Pierre