CollectionView#itemsResetted --> itemsReset

CollectionView's `itemsResetted` name always stuck out to me as grammatically awkward. I can tell that the name was meant to mirror the pattern of `itemAdded` and `itemRemoved` in that they are the past participle* of the actions "add item" and "remove item" respectively, but the [past participle of "reset"](http://en.wiktionary.org/wiki/reset) is "reset", not "resetted".

Changing the phrasing to `itemsReset` introduces a little more abiguity in that we don't have the "-ed" suffix to help determine that it's not used as a present participle, but I think its proximity to `itemAdded` and `itemRemoved` should be clear enough.

*Yup, had to look this up