Add CREDITS.md file for capturing image credits, etc.
Add CREDITS.md file for capturing image credits, etc.

ibm-watson-data-lab/ibm-watson-data-lab.github.io,ibm-watson-data-lab/ibm-watson-data-lab.github.io,ibm-watson-data-lab/ibm-watson-data-lab.github.io,ibm-watson-data-lab/ibm-watson-data-lab.github.io