Did you put this code inside the run function of your migration?

I copied your code and created a test migration, and it worked perfectly for me

<?php

use Illuminate\Database\Migrations\Migration;

class CreateTest extends Migration {

	/**
	 * Run the migrations.
	 *
	 * @return void
	 */
	public function up()
	{
		Schema::create('settings', function($table) {
			$table->increments('id');

			$table->string('name')->unique();
			$table->string('value');
			$table->enum('type', ['varchar', 'text', 'boolean'])->default('varchar');

			$table->timestamps();
		});
	}

	/**
	 * Reverse the migrations.
	 *
	 * @return void
	 */
	public function down()
	{
		Schema::drop('settings');
	}

}

This is seeder not migration