Update js-yaml to version 2. Closes gh-683.
Update js-yaml to version 2. Closes gh-683.

* I've been assured there are no breaking changes. God help me (and I'm super sorry) if that's bullshit.

coldrye-collaboration/grunt,felixgrey/grunt,abraheem/grunt,Chhunlong/grunt,r14r-work/fork_grunt_master,youmyyou/grunt,r14r/fork_grunt_master,fscherwi/grunt,imjerrybao/grunt,ThiagoGarciaAlves/grunt,shama/grunt,FeodorFitsner/grunt,paulcbetts/grunt,lkiarest/grunt,pandeysoni/grunt,IveWong/grunt,yosiazwan/grunt,paladox/grunt,zackexplosion/grunt,goodeggs/grunt,thecc4re/gruntjs,arosa81/grunt,eelve/grunt,yonglehou/grunt,q310550690/grunt,yuhualingfeng/grunt,JaKXz/grunt,thejameskyle/grunt,modulexcite/grunt,vladikoff/grunt