docs: Small tweaks to MEAN app guide
docs: Small tweaks to MEAN app guide

Clarify how to connect to MongoDB, and how to set up Quilt.

NetSys/quilt,PenguinToast/quilt,LuiseV/quilt,PenguinToast/quilt,quilt/quilt,kayousterhout/quilt,kelda/kelda,kayousterhout/quilt,quilt/quilt,kklin/kelda,LuiseV/quilt,mmussomele/quilt,ejj/quilt-dev,NetSys/quilt,LuiseV/quilt,kklin/quilt,quilt/quilt,mmussomele/quilt,LuiseV/quilt,ejj/quilt-dev,kelda/kelda,kelda/kelda,NetSys/quilt,kayousterhout/quilt,kklin/kelda,mmussomele/quilt,tejasmanohar/quilt,stevenlin598/quilt,kklin/kelda,ejj/quilt-dev,PenguinToast/quilt,PenguinToast/quilt,stevenlin598/quilt,kklin/quilt,tejasmanohar/quilt,kelda/kelda,stevenlin598/quilt,mmussomele/quilt,quilt/quilt,NetSys/quilt,ejj/quilt-dev,kayousterhout/quilt,tejasmanohar/quilt,mmussomele/quilt,PenguinToast/quilt,kklin/quilt,NetSys/quilt,kklin/quilt,stevenlin598/quilt,stevenlin598/quilt,LuiseV/quilt,stevenlin598/quilt,mmussomele/quilt,kklin/kelda,tejasmanohar/quilt