Implements division and remainder operators for vectors.

This might have been an oversight at one point. Although the `rem_v`
and `div_v` methods are available for vectors, the actual operators
were not.

Signed-off-by: Aaron Jacobs <atheriel@gmail.com>
Implements the (mutable) index operator for vectors.

Again, this is possibly an oversight. The operators simply use the
mut_i() and i() methods which are demanded by the Array1<S> trait.

This means you may access the field `x` on a VectorN with vector[0]
syntax.

Signed-off-by: Aaron Jacobs <atheriel@gmail.com>
Merge pull request #105 from atheriel/vec_ops

Actually implement division, remainder, and index operators for vectors.