Converts to using cf-core and BEM

Please note that this bumps from a minor to a major release, as such the following changes are NOT backwards compatible

Simplified dependencies by switching to cf-core which is a new Capital Framework component that combines a lot of basics like Normalize, variables, and base styles. What's also sweet is that cf-core has some handy utilities and mixins that can be leveraged.

Updated the naming conventions to use BEM. You can read more about how we use BEM in the contributing section of the CF docs.