Update CHANGELOG for v1.2.0 release
Update CHANGELOG for v1.2.0 release

Change-Id: Ie0525d300c94bfde2947b1cc2572bb7d37e17998

thdav/aom,mbebenita/aom,charup/https---github.com-webmproject-libvpx-,GrokImageCompression/aom,stewnorriss/libvpx,VTCSecureLLC/libvpx,shyamalschandra/libvpx,Laknot/libvpx,felipebetancur/libvpx,liqianggao/libvpx,kim42083/webm.libvpx,Suvarna1488/webm.libvpx,lyx2014/libvpx_c,shyamalschandra/libvpx,smarter/aom,mwgoldsmith/vpx,Laknot/libvpx,lyx2014/libvpx_c,mwgoldsmith/libvpx,shacklettbp/aom,matanbs/vp982,shacklettbp/aom,abwiz0086/webm.libvpx,sanyaade-teachings/libvpx,turbulenz/libvpx,goodleixiao/vpx,Laknot/libvpx,Maria1099/webm.libvpx,VTCSecureLLC/libvpx,abwiz0086/webm.libvpx,GrokImageCompression/aom,jacklicn/webm.libvpx,matanbs/vp982,felipebetancur/libvpx,n4t/libvpx,GrokImageCompression/aom,Topopiccione/libvpx,ShiftMediaProject/libvpx,Maria1099/webm.libvpx,n4t/libvpx,vasilvv/esvp8,shacklettbp/aom,goodleixiao/vpx,running770/libvpx,liqianggao/libvpx,mwgoldsmith/vpx,turbulenz/libvpx,matanbs/webm.libvpx,WebRTC-Labs/libvpx,jmvalin/aom,vasilvv/esvp8,shareefalis/libvpx,pcwalton/libvpx,ittiamvpx/libvpx,liqianggao/libvpx,kleopatra999/webm.libvpx,vasilvv/esvp8,WebRTC-Labs/libvpx,mwgoldsmith/vpx,jdm/libvpx,matanbs/vp982,turbulenz/libvpx,turbulenz/libvpx,jdm/libvpx,jacklicn/webm.libvpx,iniwf/webm.libvpx,jacklicn/webm.libvpx,thdav/aom,gshORTON/webm.libvpx,thdav/aom,goodleixiao/vpx,matanbs/webm.libvpx,thdav/aom,Topopiccione/libvpx,reimaginemedia/webm.libvpx,ShiftMediaProject/libvpx,mwgoldsmith/libvpx,vasilvv/esvp8,cinema6/libvpx,gshORTON/webm.libvpx,luctrudeau/aom,hsueceumd/test_hui,gshORTON/webm.libvpx,zofuthan/libvpx,shareefalis/libvpx,ShiftMediaProject/libvpx,matanbs/vp982,mbebenita/aom,cinema6/libvpx,abwiz0086/webm.libvpx,smarter/aom,felipebetancur/libvpx,iniwf/webm.libvpx,jacklicn/webm.libvpx,stewnorriss/libvpx,Acidburn0zzz/webm.libvpx,shacklettbp/aom,mwgoldsmith/vpx,Acidburn0zzz/webm.libvpx,kleopatra999/webm.libvpx,abwiz0086/webm.libvpx,thdav/aom,felipebetancur/libvpx,WebRTC-Labs/libvpx,mbebenita/aom,kleopatra999/webm.libvpx,matanbs/webm.libvpx,zofuthan/libvpx,charup/https---github.com-webmproject-libvpx-,mbebenita/aom,ittiamvpx/libvpx,running770/libvpx,kleopatra999/webm.libvpx,running770/libvpx,stewnorriss/libvpx,luctrudeau/aom,Suvarna1488/webm.libvpx,iniwf/webm.libvpx,kalli123/webm.libvpx,webmproject/libvpx,zofuthan/libvpx,Acidburn0zzz/webm.libvpx,webmproject/libvpx,shareefalis/libvpx,luctrudeau/aom,sanyaade-teachings/libvpx,lyx2014/libvpx_c,ShiftMediaProject/libvpx,luctrudeau/aom,luctrudeau/aom,kim42083/webm.libvpx,Distrotech/libvpx,matanbs/webm.libvpx,kalli123/webm.libvpx,shyamalschandra/libvpx,shyamalschandra/libvpx,pcwalton/libvpx,running770/libvpx,jmvalin/aom,sanyaade-teachings/libvpx,kim42083/webm.libvpx,altogother/webm.libvpx,kleopatra999/webm.libvpx,jacklicn/webm.libvpx,iniwf/webm.libvpx,Distrotech/libvpx,jdm/libvpx,turbulenz/libvpx,goodleixiao/vpx,mbebenita/aom,Suvarna1488/webm.libvpx,Laknot/libvpx,ShiftMediaProject/libvpx,matanbs/vp982,jdm/libvpx,webmproject/libvpx,jmvalin/aom,smarter/aom,Distrotech/libvpx,Acidburn0zzz/webm.libvpx,kalli123/webm.libvpx,cinema6/libvpx,reimaginemedia/webm.libvpx,luctrudeau/aom,pcwalton/libvpx,ittiamvpx/libvpx-1,vasilvv/esvp8,charup/https---github.com-webmproject-libvpx-,stewnorriss/libvpx,sanyaade-teachings/libvpx,Suvarna1488/webm.libvpx,jdm/libvpx,mbebenita/aom,matanbs/webm.libvpx,Acidburn0zzz/webm.libvpx,reimaginemedia/webm.libvpx,abwiz0086/webm.libvpx,hsueceumd/test_hui,altogother/webm.libvpx,GrokImageCompression/aom,pcwalton/libvpx,WebRTC-Labs/libvpx,Suvarna1488/webm.libvpx,smarter/aom,turbulenz/libvpx,Distrotech/libvpx,hsueceumd/test_hui,Distrotech/libvpx,thdav/aom,kim42083/webm.libvpx,turbulenz/libvpx,lyx2014/libvpx_c,VTCSecureLLC/libvpx,mwgoldsmith/libvpx,kleopatra999/webm.libvpx,VTCSecureLLC/libvpx,shacklettbp/aom,openpeer/libvpx_new,Acidburn0zzz/webm.libvpx,felipebetancur/libvpx,gshORTON/webm.libvpx,shareefalis/libvpx,altogother/webm.libvpx,Maria1099/webm.libvpx,ittiamvpx/libvpx,liqianggao/libvpx,turbulenz/libvpx,cinema6/libvpx,mwgoldsmith/vpx,charup/https---github.com-webmproject-libvpx-,charup/https---github.com-webmproject-libvpx-,matanbs/vp982,ittiamvpx/libvpx,gshORTON/webm.libvpx,vasilvv/esvp8,goodleixiao/vpx,webmproject/libvpx,stewnorriss/libvpx,Maria1099/webm.libvpx,ittiamvpx/libvpx-1,liqianggao/libvpx,shareefalis/libvpx,Suvarna1488/webm.libvpx,Topopiccione/libvpx,n4t/libvpx,webmproject/libvpx,openpeer/libvpx_new,ittiamvpx/libvpx-1,ittiamvpx/libvpx,iniwf/webm.libvpx,jmvalin/aom,abwiz0086/webm.libvpx,n4t/libvpx,matanbs/webm.libvpx,kalli123/webm.libvpx,iniwf/webm.libvpx,reimaginemedia/webm.libvpx,kim42083/webm.libvpx,Topopiccione/libvpx,mwgoldsmith/libvpx,zofuthan/libvpx,shacklettbp/aom,hsueceumd/test_hui,webmproject/libvpx,stewnorriss/libvpx,ittiamvpx/libvpx,kalli123/webm.libvpx,Laknot/libvpx,hsueceumd/test_hui,gshORTON/webm.libvpx,altogother/webm.libvpx,ittiamvpx/libvpx-1,reimaginemedia/webm.libvpx,openpeer/libvpx_new,altogother/webm.libvpx,zofuthan/libvpx,VTCSecureLLC/libvpx,kalli123/webm.libvpx,matanbs/vp982,jacklicn/webm.libvpx,shareefalis/libvpx,zofuthan/libvpx,kim42083/webm.libvpx,mbebenita/aom,Topopiccione/libvpx,pcwalton/libvpx,WebRTC-Labs/libvpx,cinema6/libvpx,mbebenita/aom,altogother/webm.libvpx,vasilvv/esvp8,reimaginemedia/webm.libvpx,smarter/aom,openpeer/libvpx_new,charup/https---github.com-webmproject-libvpx-,ittiamvpx/libvpx-1,openpeer/libvpx_new,mbebenita/aom,mwgoldsmith/libvpx,liqianggao/libvpx,Maria1099/webm.libvpx,mwgoldsmith/vpx,Topopiccione/libvpx,smarter/aom,GrokImageCompression/aom,jmvalin/aom,shyamalschandra/libvpx,lyx2014/libvpx_c,cinema6/libvpx,GrokImageCompression/aom,pcwalton/libvpx,running770/libvpx,lyx2014/libvpx_c,VTCSecureLLC/libvpx,jdm/libvpx,n4t/libvpx,hsueceumd/test_hui,goodleixiao/vpx,turbulenz/libvpx,jmvalin/aom,Maria1099/webm.libvpx,felipebetancur/libvpx,Distrotech/libvpx,Laknot/libvpx,ittiamvpx/libvpx-1,openpeer/libvpx_new,cinema6/libvpx,running770/libvpx,mwgoldsmith/libvpx,shyamalschandra/libvpx,sanyaade-teachings/libvpx