2.16.0

• Add Perl, Rust, TiddlyWiki, and Groovy modes.
• Dragging text inside the editor now moves, rather than copies.
• Add a coordsFromIndex method.
• API change: setValue now no longer clears history. Use clearHistory for that.
• API change: markText now returns an object with clear and find methods. Marked text is now more robust when edited.
• Fix editing code with tabs in Internet Explorer.