spectra 0.2.4

Demoscene framework
### 0.2.4

- Added `From / Into` impls for `[[f32; 4]; 4]` for `Transform`.

### 0.2.3

- `ResCache::get_proxied` doesn’t return an `Option<T>` anymore but a `T`, as it should.

### 0.2.2

- Made all `TextureImage`’s fields pub.

### 0.2.1

- Added several constructors for `Program`. Among them, `from_bufread` and `from_str`.
- Added `ResCache::get_proxied`, which takes an extra argument (regarding `ResCache::get`), a
  closure, used to compute a proxy value that will be used if resource loading fails.

## 0.2

- Added a `bootstrap!` macro used to build a `Device` in a very simple way (relying on clap).
- Fixed docs.rs link.
- luminance-glfw integration.
- Removed texture handling from the compositor and simplified it a lot.
- Switched to cgmath and dropped nalgebra.
- Refactored all spectra code according to typed programs (luminance).

## 0.1

- Initial revision.