added new logo The logo was created by the Kali Linux team and gave us permission to use it. In addition to the new logo, the ./images/ directory has been moved to into ./docs/ in order to make the root directory of the project cleaner. The old preview.png was never used as we had been using a preview image that was hosted on user-images.githubuesrcontent.com. This too has been changed so that we use the local copy instead | 
