0.7.3

This release implements the following:

• Implement feature request/issue #19 - blur only the content that is not a header, effectively revealing only the headers of any given note
• Fix an issue where the note name in the header does not reveal on hover (fixed for all modes)
• Move all hard-coded level and CSS class names to string enums for reusability and maintainability
• Refactor styles.css for better readability and maintainability
• General code cleanup

All thanks to @aurepereira !