got error : $ php artisan db:seed Seeded: UserTableSeeder Seeded: ProfessionTableSeeder Seeded: LanguageTableSeeder [BadMethodCallException] Call to undefined method Illuminate\Database\Query\Builder::associate() db:seed [--class[="..."]] [--database[="..."]]

Customer.php

<?php

class Customer extends Eloquent
{
	public function user()
	{
		return $this->belongsTo('User');
	}

	public function profession()
	{
		return $this->hasOne('Profession');
	}

	public function emails()
	{
		return $this->hadMany('customer_emails');
	}
}

gistfile1.php

<?php

class CustomerTableSeeder extends Seeder {

	
	public function run()
	{
		$ant = new Customer;
		$ant->name = 'Antoine';
		$ant->surname = 'Malpel';
		$ant->birthdate = date('1975-01-02');
		$ant->title = 'Développeur';
		$ant->gender = 'm';
		$ant->profession = Profession::first();
		$ant->nationality = 'fr';
		$ant->retirement_date = date('2066-01-02');
		$ant->comments = 'test customer (NOT REAL - DEV Purpose)';
		$ant->phone_number = '01 01 01';
		$ant->mobile_phone_number = '06 xx xx xx ';

		//$ant->save();
		$user = User::where('username', '=', 'antoine')->first();
		$user->customer()->associate($ant);
		$user->save();

/*		$profession_id = Profession::first()->id;
		$user_antoine = User::where('username', '=', 'antoine')->first();
		$user_jerome = User::where('username', '=', 'jerome')->first();

		DB::table('customers')->delete();

		$customers = [
			[
				'user_id' => $user_antoine->id,
				'name' => 'Antoine',
				'surname' => 'Malpel',
				'birthdate' => date('1975-01-02'),
				'title' => 'Développeur',
				'gender' => 'm',
				'profession_id' => $profession_id,
				'nationality' => 'fr',
				'retirement_date' => date('2066-01-02'),
				'comments' => 'test custimer (not real one)',
				'phone_number' => '',
				'mobile_phone_number' => '06 xx xx xx '

			],
			[
				'user_id' => $user_jerome->id,
				'name' => 'Jérôme',
				'surname' => 'Nicolas',
				'birthdate' => date('1971-05-06'),
				'title' => 'Gérant',
				'gender' => 'm',
				'profession_id' => $profession_id,
				'nationality' => 'fr',
				'retirement_date' => date('2066-05-06'),
				'comments' => 'test custimer (not real one)',
				'phone_number' => '',
				'mobile_phone_number' => '06 xx xx xx '

			],
		];

		DB::table('customers')->insert($customers);*/
	}
}

User.php

<?php

use Zizaco\Entrust\HasRole;

class User extends Eloquent 
{
	use HasRole;	// add permissions relation

	protected $hidden = array('password', 'confirmation_code');

	public function customer() 
	{
		return $this->hasOne('Customer');
	}
}