[DO NOT MERGE]Homepage: 1st August content update

- First and second department promos update
- Promo-image section update
- Rename the css class data to a more generic 'promo-main-text'

https://www.pivotaltracker.com/story/show/74435858
You are right, what would you suggest? Do you think that "independence referendum and what it could mean for you" should be the linked text?