update README for testem installation notes
update README for testem installation notes

nschmidtg/simpla,larryprice/ollert,leviwilson/ollert,sep/ollert,larryprice/ollert,nschmidtg/simpla,leviwilson/ollert,larryprice/ollert,nschmidtg/simpla,sep/ollert,leviwilson/ollert,sep/ollert