Initial commit to add default .gitIgnore and .gitAttribute files.
Initial
Add spiral calculation logic
End a spiral at the bottom right corner, and start just above it.
Draw the prime spiral
Darken pixels when they devide, instead of blackening them

This way you can see how primish the numbers are
Speedup by using a pixel buffer
Show the progress
Keep the pattern a bit lighter
Supply the readme with some useful info.