Update Part I: Introduction.md
Update Part IV: Arithmetic.md
Update Part II: Defining methods.md
Update Part I: MyFirstWindow.md
Update Part II: HelloWorld.md
Update Part III: Buttons.md
Update Part V: Layouts.md
Update Part VI: Text Fields.md
Update Part VII: Exercises.md
Update Part IX: Complex Interfaces.md
Merge pull request #47 from BillsJ/master

image pathways