Renamed Rectangle, so the name indicates its multiple uses.
Check size of vectors for operations that need it.
The cartesian grids now don't ignore their origin position anymore.
Add missing newline in docstring
Merge pull request #21 from Moredread/moredread/fix/vector_dimension_check

Check size of vectors for operations that need it.
Renamed nCube to Box and improved documentation
Make pypy test run optional on Tavis for now.

We know that we have unfulfilled dependencies.
Merge pull request #20 from Moredread/moredread/fix/cube

Moredread/fix/cube
Merge pull request #22 from Moredread/moredread/fix/travis_optional_pypy

Make pypy test run optional on Tavis for now.