Refined markup and CSS classes within the setup process

- Removed 'with the power of Ruby on Railsgit st' copy as it should already
  be obvious you are using Rails.
- Swapped out span's for p's for better CSS block support in the setup
  partial templates.
- Added spacing around textfields and tightened up the padding around
  the explanation text to better associate with the field.
- Refined CSS selectors to stop the clashing of the background colours
  and images.