update readme to indicate jessie image
update readme to indicate jessie image

Andrewiski/Robotics_Cape_Installer,StrawsonDesign/Robotics_Cape_Installer,StrawsonDesign/Robotics_Cape_Installer,Andrewiski/Robotics_Cape_Installer,Andrewiski/Robotics_Cape_Installer,StrawsonDesign/Robotics_Cape_Installer