Fixed syntax bug in Dockerfile.
Fixed syntax bug in Dockerfile.

orionstein/docker-ghost,orionstein/deis-ghost,mmornati/docker-ghostblog,orionstein/docker-ghost,willhackett/ghost,elisescu/docker-ghost,grieve/ghost,zedtux/ghost,Invacio/docker-ghost,MaTeamBM/docker-ghostblog,orionstein/deis-ghost,alfredkam/ghost,vitan/ghost,mshirley/ghost,joukou/joukou-docker-ghost,MaTeamBM/docker-ghostblog,coolya/ghost,dockerfile/ghost