Add v2.0 endpoint support

[DimaGershman]

Hi @HNeukermans ,
I've seen there is an old PR #27 on the same subject that looks stuck... From directly modifying the generates JS at dist/, it looks like the change is fairly minor:

instead of '/oauth2/authorize' use '/oauth2/v2.0/authorize' in UrlBuilder classes.
Of course it should be backwards compatible, so adding a parameter to AdalConfig makes sense to me.

I am sorry to admit that I gave up on making it as PR after an hour of fighting with Karma & other environment things that just wouldn't stop giving me errors from npm :(

P.S. Thank You for the library !!!