Add Markdown support

[digimezzo]

It should be possible to create and edit notes using Markdown.

[geira]

+1 for this. I've been using nvAlt on the Mac for years (and Notational Velocity before that), a Linux compatible app have been requested for years. The workflow of editing Markdown files in a single Dropbox folder works seamlessly across platforms (currently using Editorial on iOS, PlainText before that) with no sync problems. A notetaking app without multi-platform support (including mobile) and using a proprietary format will have limited appeal. So far the only option for Linux is Typora, but that is commercial software (though free in beta) and more suitable for editing single documents.

[digimezzo]

Markdown support was added.