Added tilemap.
Make tile-size public & reduce screen resolution.
Tilemap draws row @ ~320px

* We have to use multiple sprites b/c I broke out set_position() and draw()
* (Should probably merge them so I can reuse single sprite.)
Add little obstacle course to the test map!

Conflicts:
	src/map.rs
Use tile shown in ep-011
Move set-position before draw so we can use a single sprite.