Document change in side effect of map.invalidateSize()

[jieter]

While investigating jieter/Leaflet.Sync/issues/4, it took me some time to find out that in Leaflet 0.6.x map.invalidateSize() fires no move event anymore if the size did not change.

The name of the method and the documentation did not suggest it did, but implementations might rely on it. A small note in the changelog might save time in those cases...

[mourner]

Yep, sorry! I just didn't think someone would use invalidateSize for that as the name of the method suggests different use cases (size-related). :)