Vector2 and Vector3 has tests in ruby, so I thought that add this type of test to Vector4 make the API more consistent.

To make these tests a interface to be used with SWIG is needed, so it consists essentially in create Vecto4.i (interface) and Vector4_TEST.rb (ruby test) files.

I suspect that the ruby tests are used in CIs of other platforms, and would like to know more about they and the use in the application.