Updated to latest rust
* Added Cargo.toml and restructured project to match Cargo layout
* Simplified error.rs
* Updated to new ptr syntax (`*const`)
Cleanup some files
Fixed some compiler warnings
Updated author list
Flexibly determine demo.ocl location
Removed superfluous lifetime
Moved read_write back to passing references
Revert api change
Merge pull request #39 from mathijshenquet/master

Update to latest rust.