Adding hw04
Adding lecture08
Merge branch 'master' of https://github.com/AllenDowney/SoftwareSystems
Merge branch 'master' of https://github.com/AllenDowney/SoftwareSystems
Implemented strjoin
Adding exam1
Merge branch 'master' of https://github.com/AllenDowney/SoftwareSystems
Exam 1 commit: Solutions to 3.1 and 3.2