Remove refactoring notes and update version to 2.1.0 following the complete transition to ANTLR 4 parser. All existing functionality remains intact and backward compatibility is maintained.

Author: feihoo87

REFACTORING_NOTES.md

@@ -1,2 +1,2 @@
 """Define version number here and read it from setup.py automatically"""
-__version__ = "2.0.2"
+__version__ = "2.1.0"