Eme Versions Save

Bug fixes:

• Fix path to github-markdown-css, related to an export as PDF error
• Refactor make-html helper

New feature:

• Export as PDF
• Build for Windows

macOS prebuilt(pre-release) is now available

• Change folder structure
• Add icons

• bug fixes
• tab style tweaks
• add writing modes
• add vim mode

Bug fixes:

• Press x only close window
• CMD+Q will quit app but still asking user for saving unsaved files.