Pullrequest version

The current version of rustray does a lot of useless copying in the raytracer, which made it rather slow. I have made some changes to make it use borrowed pointers, which speeds it up significantly (tracing the example image now takes 0.36 seconds on my machine, as opposed to about 20 minutes when using the original code).

There are some other minor changes, such as vec::len(somevec) being replaced by somevec.len() and vectors being created with the required capacity in cases where this is known in advance.