[motherhamster] aligned tiles have gaps

[Bob the Hamster]

Check out the latest sidescroller code. Even though the 16x16 dirt tiles 
are aligned neatly, gridlines show up between them. The width of the 
gridlines varies depending on camera alignment.

Even if I edit the display.render line in the DirtTile class in dirty.py 
and add something like scale=1.05 to make the lines go away, they are 
still visible when moving.

I am thinking that this might have something to do with the fact that I 
am using a floating point vector for camera position, but I am really 
not sure what to do about it... Any ideas?

---
James