v0.7.0-dev.4

• New extension Iterable.toImmutableList(): KtList
• New extension Iterable.toImmutableSet(): KtSet
• New extension KtIterable<num>.average(): double
• Relax sortBy/sortByDescending, maxBy/minBy typing to work better with ints and doubles

// Was: int doesn't not implement Comparable<int> but Comparable<num>
// minBy therefore required some help to figure out the correct type (<num>) 
users.minBy<num>((it) => it.age);

// Now: minBy doesn't require the Comparable (num) to have the same same as the value (int).
users.minBy((it) => it.age);