Make tests pass after adding new DocumentController
Refactor: add TextDocument.has_real_path
Fix setup for OS X 10.9

These changes are probably less related to 10.9 than they are to the general progress of newer versions of dependencies.
Implement UndoManager supporting savepoints
Finish implementing TextDocument.save
Implement document saving, including UI
Fix application startup bugs

Editing a document causes crash...
isDocumentEdited -> is_dirty
Fix crash on edit
UndoManager.has_unsaved_changes change events
Move TextDocument init code out of Application
Fix KVO propagation from document to editor
Fix crash on quit
Fix undo support
Fix document dirty status indicator updates
Minor refactor of OpenPathController
Prompt to save dirty documents on quit
Fix test slowdown from previous commit
Reasonable defaults for syntax definition

Plus other minor cleanup
Implement Editor.interactive_close()