Update image urls
Update image urls

The repo's name changed and for a while, the gh-pages assets still worked, but apparently github recently un-published the old url and didn't bother with publishing the new one. So, the fix was first to make a change to the gh-pages branch to get it updated, and then to update the readme to point to the correct repo name.

Fixes #2
watson-developer-cloud/rpi-time-weather-demo,watson-developer-cloud/rpi-time-weather-demo,watson-developer-cloud/raspberry-pi-time-weather-demo,watson-developer-cloud/raspberry-pi-time-weather-demo