Fix image URL in README after moving the repo to an organization.
Fix image URL in README after moving the repo to an organization.

spt/spitfire,youtube/spitfire,nicksay/spitfire,spt/spitfire,nicksay/spitfire,spt/spitfire,youtube/spitfire,spt/spitfire,nicksay/spitfire,youtube/spitfire,nicksay/spitfire,youtube/spitfire