add changelog for ver 1.2.0
add changelog for ver 1.2.0

kimchouard/jsforce,jsforce/jsforce,saleswise/jsforce,jesperkristensen/jsforce,pcon/jsforce,saleswise/jsforce,jdcrensh/jsforce,joeferraro/jsforce,bhaskarmelkani/jsforce,lkatney/jsforce,saleswise/jsforce,jsforce/jsforce,joeferraro/jsforce,parthiban019/jsforce,rdietrick/jsforce,pcon/jsforce,parthiban019/jsforce,lkatney/jsforce,nutthawan/jsforce,bhaskarmelkani/jsforce,jesperkristensen/jsforce,jdcrensh/jsforce,pcon/jsforce,jsforce/jsforce,nutthawan/jsforce