title: create/drop database task for gulp/knex
body: <p>I have an Express.js web applications which uses Knex.js as the SQL query builder and migrations engine.
  While Knex.js has methods for creating, dropping, and altering tables, it doesn't have methods for creating/dropping the database itself.</p>
  
  <p>I was wondering if there is an extension for Knex.js or even a gulp task that allows you to create/drop a database. I couldn't find any.
  I'm using a PostgreSQL database.</p>