3.1.0

• Incompatible: key handlers may now return, rather than throw CodeMirror.Pass to signal they didn't handle the key.
• Make documents a first-class construct, support split views and subviews.
• Add a new module for showing completion hints. Deprecate simple-hint.js.
• Extend htmlmixed mode to allow custom handling of script types.
• Support an insertLeft option to setBookmark.
• Add an eachLine method to iterate over a document.
• New addon modules: selection marking, linting, and automatic bracket closing.
• Add "beforeChange" and "beforeSelectionChange" events.
• Add "hide" and "unhide" events to marked ranges.
• Fix coordsChar's interpretation of its argument to match the documentation.
• New modes: Turtle and Q.
• Further improvements to the vim mode.
• Full list of patches.