make oauth2 function call promised
make oauth2 function call promised

nutthawan/jsforce,bhaskarmelkani/jsforce,joeferraro/jsforce,pcon/jsforce,nutthawan/jsforce,joeferraro/jsforce,pcon/jsforce,parthiban019/jsforce,rdietrick/jsforce,jdcrensh/jsforce,kimchouard/jsforce,lkatney/jsforce,lkatney/jsforce,jesperkristensen/jsforce,bhaskarmelkani/jsforce,parthiban019/jsforce,jdcrensh/jsforce,saleswise/jsforce,saleswise/jsforce,jesperkristensen/jsforce,jsforce/jsforce,pcon/jsforce,polidog/jsforce,stomita/node-salesforce,jsforce/jsforce,jsforce/jsforce,saleswise/jsforce