Add validations to validate the presence of a user's first name, last name, and profile name.

  validates :first_name, presence: true
  validates :last_name, presence: true
  validates :profile_name,presence: true

class User < ActiveRecord::Base
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable

  attr_accessible :email, :password, :password_confirmation, :remember_me,
                  :first_name, :last_name, :profile_name

  validates :first_name, :last_name, :email, :profile_name, :password, presence: true

  validates :profile_name, uniqueness: true,
                               format: {
                                  with: /^[a-zA-Z0-9_-]+$/
                               }

  def full_name
    first_name + " " + last_name
  end
end