async changePassword (uid, newPassword) {
    const password = bcrypt.hashSync(newPassword, bcrypt.genSaltSync())

    const result = await db('users').where('id', uid).update({
      password: password,
      token: randomString.generate(32),
      lastSeen: (new Date()).getTime()
    })

    return result
  }
Change user's password

@param {Int} uid user id
@param {String} newPassword new password

@returns {Int}