Add postinstall script to fetch data. Update doc.

[tiagojdf]

I have added a postinstall step to the package.json, this way the script is run to update the database. I have also updated the docs.

[rexxars]

This looks great! I'm a bit skeptical to running the script on postinstall though - it makes deployment and updating dependencies etc a bit weird. If you rename the npm script to something else and document the use/setup of it, I'd happily merge this.

[tiagojdf]

Updated. Let me know if you want me to change anything.

[kbrabrand]

:+1: