Adding hw03
Adding test1.c
Adding lecture11
Merge branch 'master' of https://github.com/AllenDowney/SoftwareSystems
Adding hw04
Adding hash.c
Merge branch 'master' of https://github.com/AllenDowney/SoftwareSystems
Adding lecture12
Adding check_uniform
Merge branch 'master' of https://github.com/AllenDowney/SoftwareSystems
Adding lecture13
Merge branch 'master' of https://github.com/AllenDowney/SoftwareSystems