Update styles for cleaner look

The red is a bit harsh and cleaner typography could help. Also, considering trying to add styling to the "ad-detector" badge (so that it's more official) and "X" button is more of a button and intuitive to the user. 

[Full disclosure: I'm an Art Director for The Atlantic and we think about these things a lot from a readers perspective. I love this idea and would like to help develop a standard that balances user experience with full transparency]