Take params by value in impls of arithmetic op traits

Arithmetic op traits in Rust have been changed to take params
by value instead of by ref.
Have vertex_arrays example build

Due to a recent Rust change, macros that return items must be
either terminated with a semicolon, or wrapped in braces.

A macro contained in this example does not satisfy this requirement.
Since it is unused, we simply remove it.
Merge pull request #62 from crumblingstatue/master

Update to build with latest Rust