Bumping version to 0.4.0rc6 and publishing to npm.
Bumping version to 0.4.0rc6 and publishing to npm.

* Updating grunt/gruntplugin dependencies to rc6.
* Changing in-development grunt/gruntplugin dependency versions from tilde version ranges to specific versions.

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