Dlc 17 - Listings UI [IN-PROGRESS]

@Saityi make a pull request next time and tag me. Don't be shy :)
Any of the following introduce an error:
`render 'admins/show'` (NoMethodError) 
`redirect_to 'admins/show'` (No data received error)
`redirect_to @admin` (Cannot redirect to nil!)
`render @admin` (Missing template listings/destroy)

I think the listings controller's destroy is having trouble seeing anything related to admin. I couldn't find a better solution than this. `redirect_to :back` simply reloads the page and, looking around, appears to be the most common way of reloading a page.