code: function FBOAuth2(appId, appSecret, redirectURL){
    this._appId = appId;
    this._appSecret = appSecret;
    this._redirectURL = redirectURL;
    this._authURL = 'https://www.facebook.com/dialog/oauth';
    this._graphAPIURL = 'https://graph.facebook.com';
    this._accessTokenURI = '/oauth/access_token';
    this._profileURI = '/me';
  }
docs: Facebook OAuth2 object, make various requests
  the the graphAPI
  @param {string} appId     the facebook app id
  @param {string} appSecret the facebook app secret
  @param {string} redirectURL  the url facebook should use as a callback