Left 4 Pop v0.3 Update

Gave the editor a try again with the new fixes, and found a few things:
* Sidewalk-road curved corner piece appears slightly lower in the editor than it will be when playing the level.
* Sidewalk appears slightly higher in the editor than it will be when playing the level. (Tried this out by placing a decorative on sidewalk and see if a gap appeared under it when playing.)
* Found a way to consistently cause zebra crossing road to duplicate when it shouldn't:
   1. Try to duplicate (ctrl + D) an existing zebra crossing road piece. (But it will not duplicate)
   2. In the TAB drawer menu, click the zebra crossing to place another one.
   3. Deselect the newly placed road piece.
   4. Select it again and move it a bit. A duplicate should have appeared.

Gave the map editor a try, and maybe encountered a few bugs and/or unintended features:
* Zebra crossing road doesn't duplicate with ctrl + D (but other things do so just fine).
* Zombies walk through certain cars (police car and yellow pickup).
* Used a combination of different roads all placed at the same y level (-0,1), but when transitioning from walking on a road with center marking ( - - - - ) to walking on a plain road it moves the player down a little, even though it appears level.
* Placing more spawners seems to increase wave size or spawn rate?
* At the start of a custom level, it looks like the player doesn't start at the player start position, but is moved there after the first second or two.