Remove weather card; make hero image show sun (eventually to show current weather cond)
Fix for https://bugzilla.mozilla.org/show_bug.cgi?id=1023975

The problem is that addCard is being called from the result of a background thread doing an HTTP request. This NPE occurs when the following steps happen:

1) Fragment exists
2) HTTP call starts
3) Fragment's onDestroyView occurs
4) HTTP call completes