Adding solution
Adding Sync.py
Quick fix
Adding lecture 14
Log2 scale
Merge branch 'master' of https://github.com/AllenDowney/SoftwareSystems
Bug fix in Sync.py
Adding lecture15
Adding hw04 soln
Adding code for quiz 4
Merge branch 'master' of https://github.com/AllenDowney/SoftwareSystems
added insert_by_index function