adding cta for signup and video
fixing classes and formatting
Merge pull request #39 from gocardless/features-cta

adding sign up and video cta to /features
cetering ctas
Merge pull request #40 from gocardless/features-center-fix

Centering the new cta's
Fixing broken link
Merge pull request #41 from gocardless/how-to-link-fix

Amending copy & href of FAQ link on /how-to
Merge branch 'dev'