Update to ggez devel branch (0.5.0)

[icefoxen]

This will take work. Firstly, I want to use euclid for it, and that needs mint integration:

• https://github.com/servo/euclid/pull/205
• https://github.com/kvark/mint/issues/29
• https://github.com/kvark/mint/issues/30

There doesn't seem to be anything BLOCKING this currently, it just needs doing.

Secondly that we need to make Everything Work, since the last time it really did was ggez 0.3. Camera, input and scene will be the easy parts. particle and bitmap_font will take a bit more work.

Thirdly, we need to polish this up and make it a real crate. This needs:

• version numbers (matched with ggez???)
• Documentation
• Examples
• Proper dual license
• #[deny(missing_docs)] and all those other useful things

[icefoxen]

Based off the latest 0.5.0 release, after that happens.

Features to have:

• [ ] Make particles suck less
• [ ] Make sure camera and bitmap font still work, remove them if not.
• [ ] #16 Pop-multiple (question is, how do we return original scenes? heck, just return a Vec)
• [ ] #15 Make input bindings simpler/better (ggez now handles input states as well, but we have Axis abstractions with interpolation, so....)
• [ ] #10 Whatever else