Update README.md

The Mongo instructions did work, but the instructions were
a little bit unclear.  I also noticed that the db directory
has all the scripts needed to re-create the site.  Hopefully
this helps.
Merge pull request #114 from dsyer/patch-1

Update README.md
Improve instantiation of mongo.json file.
Minor tweaks to README.md
Strip out isolated_mode configuration.
Issue 106 108: which command breaks zsh in init snippet.
Updates to 0.9.5 mongo script.