Add PropTypes to card and button patterns

[barrymcgee]

Done

• Added defaultProps and propTypes to existing components.

QA

• Pull code
• Review code for sanity
• Run npm run start
• Navigate to http://localhost:3000
• Check no console errors
• Run npm run lint
• Check no errors except the error outlined in #17

Fixes #16

[webteam-app]

No ./run found. Unable to start demo.

[barrymcgee]

@Lukewh I should have actioned all your suggestions here, would you mind casting another eye over? Many thanks :)