Move py_to_notebook.py to bin/ directory for better organization

- Moved tools/py_to_notebook.py to bin/py_to_notebook.py
- Updated tito.py to reference the new location
- Made py_to_notebook.py executable for direct invocation
- Removed empty tools/ directory
- Updated documentation to reflect new location
- All tools now consolidated in bin/ directory for consistency

Benefits:
- Conventional organization (bin/ for executables)
- Can invoke tools directly: ./bin/py_to_notebook.py
- Cleaner project structure
- Consistent with other tools (tito.py, generate_student_notebooks.py)

docs/development/module-development-guide.md

@@ -208,7 +208,7 @@ python bin/tito.py notebooks --module {module}
 
 ### Generate Student Version
 ```bash
-python3 bin/generate_student_notebooks.py --module {module}
+python bin/generate_student_notebooks.py --module {module}
 ```
 
 ### Test Complete Workflow