Marcel 0.2.0

• Adds support for .js data files (#42).
• Adds build (default) and serve commands to the CLI (#22).
• Adds support for sync/async custom filters (#43). For this, we switched to async rendering for Nunjucks.
• Adds the format_date filter.
• Adds the sort_by filter to sort lists of posts by property. Added sorting by date. Fall back .date and .updated to file attributes. (#33)
• Posts that have draft: true in their front-matter will not be built / served by default. Pass in -d or --drafts to the CLI commands to include the draft posts. (#41) Posts that have permalink: false in their front-matter will not be included in the build.
• Posts that have their slug / permalink ending in .html will not get /index.html appended to them.