Fix some typos in lecture 06
Merge pull request #41 from mdimitrova/06-fix-typos

Fix some typos in lecture 06
Fix a syntax error in slide 41
Merge pull request #44 from mignev/05-fix-typo

Fix a syntax error in slide 41
Fix various minor typos/mistakes

Conflicts:
	lectures/06-classes-namespaces-inheritance.slim
Clarify slide about global namespace access