Codelab: Pearl's updates to Ahmad's updates

Changelog:
- 2nd sweep for 0.9.0-1 breaking changes
- Swapped Step 9 and Step 10
- Cleaned up some screenshots for clarity
Merge branch 'codelab-fixes-pearl' of github.com:pearlchen/yeoman.io into pearlchen-codelab-fixes-pearl

Conflicts:
	app/codelab/write-unit-tests.md
Merge branch 'pearlchen-codelab-fixes-pearl' into codelab-fixes