[suggestion] Add KNEX format output

#1

I use knex to define and seed a test database.

A single line of test data looks like this ;

  knex('posts').insert({
    "_id": "57266a80-39a0-4c4d-a574-fe268cc754eb",
    "title": "Director of Sales",
    "content": "Maecenas leo odio, condimentum id, luctus nec, molestie sed, justo. Pellentesque viverra pede ac diam. Cras pellentesque volutpat dui.\n\nMaecenas tristique, est et tempus semper, est quam pharetra magna, ac consequat metus sapien ut nunc. Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia Curae; Mauris viverra diam vitae quam. Suspendisse potenti.",
    "views": 375
  }),

It’d be really cool if you’d add that to your list of export format types!