text: exports.up = function(knex, Promise) {
    return knex.schema.createTable('sentences', tbl => {
      tbl.increments()
      tbl.integer('group_id').notNullable().references('groups.id').onDelete('CASCADE')
      tbl.boolean('completed').defaultTo(false)
      tbl.integer('winner').references('users.fbid')
      tbl.text('post_url')
    })
  };
  
  exports.down = function(knex, Promise) {
    return knex.schema.dropTable('sentences')
  };
  