Balzac for Siteleaf v1.0

• ported Jekyll theme to Siteleaf
• greatly simplified template system, reducing to one for pages and one for posts (feature/no-feature/light-feature templates can be used through metadata feature and dark)
• refactored layout code to wrap content instead of including separate head/footer includes on every template
• removed head-dark include by adding dark metadata field
• extracted comments and sharing snippets to includes
• replaced complex excerpt template code with Siteleaf's excerpt variable
• removed Entypo icons from repo and replaced with links to Symbolset CDN
• removed all images (feature images should be uploaded to Siteleaf site to decouple from codebase)
• added Guardfile to watch SASS files and compile/compress when changed