Moves EXTDocument internal state to a class extension.
nonatomic properties in EXTDocument
Removes #import "EXTView.h" from EXTDocument.h.
Removes explicit backing instance variable declarations and @synthesize. Replaces direct instance variable access with property accessor methods.
Converts extview from an instance variable to a declared property.
Avoids setters in -[EXTDocument init].
Adds a newline at the end of EXTDocument.h.
Merge pull request #3 from bavarious/modernEXTDocument

Modernises EXTDocument
little fix to todo.md