Document or Change Postgres binary dependency

[jrnt30]

First, thanks for the project, it looks very compelling. As I was trying to go through the tutorial, I ran into an issue with the DB Migration process. I had started my Postgres DB in a docker container (and did not have this Postgres driver itself natively installed on my machine) and received:

Error: couldn't create database footnotes-buffalo_development: error creating PostgreSQL database footnotes-buffalo_development: exec: "createdb": executable file not found in $PATH:

It turns out after installing Postgres client (and the related binaries) things "just worked".

Ideally there would be no need for the Postgres tool chain at all to be installed locally at all, but it would be handy I think to explicitly call this out.

I haven't had time to look into this further, but if this is also a requirement for any specific type of migrations, then it would make the case for native support in the tool even more compelling to remove the dependency for CI systems, containers, etc. to package that.