update README timeline
update README timeline

jhilde/studentinsights,jhilde/studentinsights,studentinsights/studentinsights,jhilde/studentinsights,hunterowens/somerville-teacher-tool,erose/studentinsights,codeforamerica/somerville-teacher-tool,codeforamerica/somerville-teacher-tool,codeforamerica/somerville-teacher-tool,hunterowens/somerville-teacher-tool,erose/studentinsights,studentinsights/studentinsights,hunterowens/somerville-teacher-tool,erose/studentinsights,jhilde/studentinsights,studentinsights/studentinsights,studentinsights/studentinsights,codeforamerica/somerville-teacher-tool,erose/studentinsights