Hide collection view cell upon selection

[calebrudnicki]

Proposing a small addition to this repo to make the cell's transition feel more like it is becoming a part of the image view on the detail view controller. Airbnb does this trick as well by making the cell disappear after it is selected.

Here is a side-by-side demo from Airbnb and this project (after the changes):

[tungfam]

@calebrudnicki very great suggestion! looks nice ;)

I'll have to edit the tutorial before I can merge this :) since as you may have seen I have these bullets with numbers and to not confuse anyone I would need to add a new bullet to it.

Will merge later :) many thanks!