Update to rxjs beta.6

[jeffbcross]

Going to skip rxjs beta.1 since the beta.2 release expected soon. There was a cascading test failure when upgrading to rxjs beta.1 related to an angular2 test that actually should already be failing, but the exception is being swallowed because of exception-swallowing behavior in rxjs beta.0.

[jeffbcross]

BTW here is the test that starts failing (which cascades to make many tests fail):

angular/modules/angular2/test/core/zone/ng_zone_spec.ts

Line 252 in 05238df

it('should run subscriber listeners in the subscription zone (outside)',

[jeffbcross]

Waiting on #8003 and then I will update to RxJS beta.6