Create a custom table view cell to show feed info
Define a protocol for feed table's data source

This protocol essentially wraps two existing protocols
provided by UIKit: UITableViewDataSource and
UITableViewDelegate. In addition, it also defines one
more method that's required.
Provide a default impl of feed table data source protocol
Create a view controller that manages feed list table
Add SDWebImage library as a dependency

We'll be using this library to asynchronously fetch
images associated with a feed.
Add feed placeholder image

This image will be used instead if the image for
a feed couldn't be downloaded.
Tell SDWebImage to load feed image asynchronously