Moved PrimitiveType from Mesh into *Slice
#[packed] -> #[repr(packed)]
Merge pull request #272 from bjz/fix-tests

#[packed] -> #[repr(packed)]
Merge pull request #271 from sectopod/slice

Moved PrimitiveType from Mesh into *Slice
Remove Color type to make ClearData cleaner

We can't currently derive from fixed length arrays, but I think it's better to have an API that is consistent with our goals of mathematics library agnosticism.
Merge pull request #274 from bjz/remove-color-type

Remove Color type to make ClearData cleaner
Clean up examples

- Use rust-style field names for `#[shader_param]` and `#[vertex_format]` structs
- Pass the model, view, and projection matrices into the shaders separately
- Remove pointless setting of `.x.x` matrix element
- Clean up formatting