Adding hw04
Merge branch 'master' of https://github.com/AllenDowney/SoftwareSystems
Adding hash.c
Merge branch 'master' of https://github.com/AllenDowney/SoftwareSystems
Add results of no2 in hw03.
Add clean to Makefile.
Modify code to test my_random_float2().
Implement almost all feature of 'insert.py' but it occurs a memory error now.
Finished implementing and ingested all the data to DB.