Use a context manager
Added housing and civic buildings, not currently used
Add people to living space, currently everyone is homeless
Display number of homeless people
Randomise death and increase speed slightly
Add GPL headers to new files
Python 3 support
Improve performance and making ticks more stable

Previously we printed stats every len(people) per tick, which ate a lot of CPU time

We now use a timer thread, giving ticks a stable minimum time
Cims with less than 50 health will not reproduce
Merge pull request #2 from moggers87/housing

Some old changes and initial code for housing and civic buildings (e.g. education and healthcare)