insert! semantics when index > length(collection)+1

[simonster]

When insert!(collection::Vector, index, item) is passed index > length(collection)+1, insert! goes ahead and inserts the item, and the elements in between the old end of the vector and index are uninitialized memory. Personally I think it would be safer to throw a BoundsError for this case, but if we leave things as is, we should document this.

[JeffBezanson]

A BoundsError in that case sounds like a good idea.