Remove `renderAndInsertItem`

This is extremely simple one-line shortcut without side effects that can be replaced by similar simple code. I removed it because there are a lot of methods in collection-view already.
Rename `getView` to `initItemView`.

There’s `getItemViews` which sounds the same but does the opposite and new name clearly represents what method does: it just initialises new instance of child view.
Remove Collection#addAtomic.
CollectionView: clear up grammar in itemsResetted --> itemsReset
Merge pull request #440 from akre54/items-resetted

CollectionView#itemsResetted --> itemsReset
Merge pull request #438 from chaplinjs/topics/remove-add-atomic

Remove Collection#addAtomic.
Update changelog.
Rename collection view’s `showHide*` to `toggle*`.

Toggle is a good analog of jQuery.fn.toggle() [although jquery.toggle behaves not like our version — it allows to pass boolean params to show-hide and is not event handler like our version, so it would be strange].
Merge pull request #437 from chaplinjs/topics/clean-collection-view

Clean up collection view
Update CHANGELOG.md
Update collection view docs.
Merge remote-tracking branch 'origin/master' into topics/composer
Merge branch 'topics/composer' of github.com:chaplinjs/chaplin into topics/composer
Fixed various things; added more tests; allow override Composition.