Update to latest rust

[mathijshenquet]

Hello luqmana,

I updated rust-opencl to the latest rust version, and added Cargo support. I also took the liberty of adding your email address to the Cargo.toml manifest, I hope you don't mind. I also managed to significantly simplify error.rs.

Thanks for the great library!

[luqmana]

Awesome! Mind adding some more to the authors list (and yourself too):

    "Colin Sherratt <colin.sherratt@gmail.com>",
    "Eric Holk <eholk@cs.indiana.edu>",
    "Ian Daniher <it.daniher@gmail.com>",
    "Luqman Aden <me@luqman.ca>,
    "Milinda Pathirage <milinda.pathirage@gmail.com>",
    "Sébastien Crozet <developer@crozet.re>"

Thanks @mathijshenquet !

[mathijshenquet]

Great!

I added the authors and cleaned up some stuff, it is should be ready to merge now.

[luqmana]

Thanks!