Docs: add basic docs on DL4J + cloud computing

[AlexDBlack]

Basically: "if you are new to cloud computing and want to run DL4J using it, here are the options, now go and read this"
i.e., link to resources to help people get started and understand what they should be researching.

This would be a starting point for those people who have never used AWS, don't know what EC2 is, etc. but need more hardware than they have available for training their networks.