Updates for v4

[jimmynotjim]

Updated the source files to work with the v4 release of Capital Framework, including the unmerged changes in Capital Framework PR #449

Changes

• Updated the theme overrides for v4 variable changes
• Updated the example index page for v4 markup changes

Testing

• Sym-link the generator by running npm link in the repo root
• In an empty test directory run yo cf, follow the prompts
• Open the index page in a browser and test the components (Note: You'll need to fix some file paths to get this to work, it's a lot easier with the http-server setup in #134)

Review

• @Scotchester
• @cfarm
• @contolini
• @anselmbradford

Checklist

• [x] Changes are limited to a single goal (no scope creep)
• [x] Code can be automatically merged (no conflicts)
• [x] Code follows the standards laid out in the front end playbook
• [x] Passes all existing automated tests
• [x] New functions include new tests
• [x] New functions are documented (with a description, list of inputs, and expected output)
• [x] Placeholder code is flagged
• [x] Visually tested in supported browsers and devices
• [x] Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)

[jimmynotjim]

I'm gonna merge this since I've tested it a bit and I'd rather this project not get too outdated.