v0.9.1

• #138 Deprecate KtIterable<T>.sumByDouble in favor of KtIterable<T>.sumBy which now works for int and double
• #140 KtMap.getOrDefault now returns V instead of V?
• #140 Fix KtMap.groupBy returning KtMap<K, KtMutableList<T>> instead of KtMap<K, KtList<T>> causing generic type problems in further processing