Added a package.json, simplifies install instructions to just 'npm install'

Adding a package.json means that running `npm install` will install all dependencies mentioned in the `dependencies` and `devDependencies` field. I added `connect` as a dev dependency, but the distinction isn't meaningful beyond aesthetic unless you package and publish `jot` as a npm module.

I updated the README to use a single `npm install` command, and to remove the extra command before setting up the editor.