fix #50 `mean docs` open learn.mean.io
fix #50 `mean docs` open learn.mean.io

SibuStephen/mean-cli,linnovate/mean-cli,SibuStephen/mean-cli,Jeff-Lewis/mean-cli,Jeff-Lewis/mean-cli,Jeff-Lewis/mean-cli,SibuStephen/mean-cli,linnovate/mean-cli,linnovate/mean-cli