Fix invalid UTF-8 character; fixes build error with SED
Ticket #176: Changed `me.ColorLayer`, `me.ImageLayer`, and `me.TMXLayer` to inherit from `me.Renderable`
Ticket #176: Fix `inViewport` property for `me.Renderable` class
Ticket #176: Fix some property collisions on TMX classes now that they inherit from `me.Renderable`

- Also make other TMX classes inherit from `me.Renderable`
- Fix `inViewport` property
- Change platform example to use `inViewport` to detect falling off the screen, instead of checking object position.