Import Carbon components

[kellychurchill]

Carbon React components and styles must be imported to be used in creating a Gatsby site. Suggest copying from ibm-frontend/gatsby-starter-carbon--deprecated#6

This issue is complete when:

• carbon-components-react is a dependency in this repo
• Carbon's stylesheet are imported into the demo page
• Importing Carbon React components is straight forward without having to dive deep into node_modules for import paths (Import path resolving)

[kellychurchill]

This starter uses Styled Components. We will need to remove them and import the styles sass file and add node-sass (sass-loader?)
Remove Styled Components from the README