4.0.0

• Feature: adds ability to pass configure as nunjucks.Environment.
• Fixed: all errors are sent into compilation.errors now.
• Fixed: use fs-extra to output file when writeToFileEmit: true.
• Changed: rename option from writeToFileWhenMemoryFs to writeToFileEmit.
• Changed: all templates now always emitted in webpack assets.
• Changed: rename options from template to templates.
• Changed: option templates should be always array.
• Removed: webpack@1 support.
• Refactor: simplify code.