0.4.0-rc.1

What's Changed

• Changed to json encoding for compile_string by @bcardarella in #89
• Support pretty option by @bcardarella in #91
• Allow for special keys in stylesheets by @bcardarella in #92
• Encode nil by @bcardarella in #93
• Ensure formatted json encoding for nil by @bcardarella in #94
• Enhance stylesheet recompilation strategy by @bcardarella in #96
• Add stylesheet safe lists by @bcardarella in #97
• Add stylesheet safe lists by @bcardarella in #98

Full Changelog: 0.3.1...0.4.0-rc.1