tokenNotExpired don't use tokenName from AuthConfig

[RicardoRFaria]

Hi guys, I'm using angular2-jwt and I realized that when I call tokenNotExpired without provide a tokenName he uses 'id_token' as you can look here:
var authToken:string = tokenName || 'id_token';

I think that angular2-jwt should use token name from AuthConfig instead a fixed value.

[chenkie]

Agreed :) this will come in a later release. #11 touches on the same issue.

[RicardoRFaria]

Ok, I'll close this in favor of #11