Vanilla registry (no replication)

I wanted to set up a vanilla registry without replicating the main npm registry.

I had to make a some simple changes, mainly to rename `_design/scratch` to `_design/app` and configure `secure_rewrites`.

In addition, I found out that the vhosts configuration does not appear to be optional any longer so have updated the README to reflect that.

I added the .gitignore for node_modules but you may prefer to push them to the repository.