TranslateService.stream premature translation

[fjozsef]

I'm submitting a ... (check one with "x")

[x] bug report => check the FAQ and search github for a similar issue or PR before submitting
[ ] support request => check the FAQ and search github for a similar issue before submitting
[ ] feature request

Current behavior
TranslateService.stream can miss language changes when there has not been subscribed to the Observable created of it.

Expected/desired behavior
TranslateService.stream shouldn't make the first translation when it is called. Only when someone is subscribing to its Observable.

Reproduction of the problem
http://plnkr.co/edit/iI7WDj9ht9xwHbLPNNrz
The french translation should be shown, but the english text is displayed.

Please tell us about your environment:
See in plunker.

Known workaround
Wrap the Observable created by stream with defer.