dimension inputs for box requires separate variables rather than a vector

**Issue by [burdickjp](https://github.com/burdickjp)**
_Friday Apr 15, 2016 at 13:07 GMT_
_Originally opened as https://github.com/dcowden/cadquery/issues/141_

----

I would like to feed box a vector for x,y,z dimensions rather than having to explicitly state x,y,z variables. Something like:
dim = [2, 1, 1]
result = cadquery.Workplane("XY").box(dim)

rather than having to do this:
result = cadquery.Workplane("XY").box(dim[0], dim[1], dim[2])