Add Ruby interfaces to all classes

[chapulina]

Desired behavior

We should complete our Ruby scripting support for all classes. Now that we have SWIG -based Python interfaces for all classes, it should be quick to migrate them to Ruby.

We should also add tests for all classes.

Alternatives considered

Abandoning Ruby in favor of Python?

Implementation suggestion

It should be quick to port the existing SWIG files to Ruby. Adding tests will take longer.

The files live here: https://github.com/ignitionrobotics/ign-math/tree/ign-math6/src/ruby

Here's the status:

1. Angle
2. AxisAlignedBox
3. Box
4. Color
5. Cylinder
6. DiffDriveOdometry
7. Filter
8. Frustum
9. GaussMarkovProcess
10. graph/Edge
11. graph/GraphAlgorithms
12. graph/Graph
13. graph/Vertex
14. Helpers
15. Inertial
16. Kmeans
17. Line2
18. Line3
19. MassMatrix3
20. Material
21. MaterialType
22. Matrix3
23. Matrix4
24. MovingWindowFilter
25. OrientedBox
26. PID
27. Plane
28. Pose3
29. Quaternion
30. Rand
31. RollingMean
32. RotationSpline
33. SemanticVersion
34. SignalStats
35. Sphere
36. SphericalCoordiantes
37. Spline
38. Stopwatch
39. Temperature
40. Triangle3
41. Triangle
42. Vector2
43. Vector3
44. Vector3Stats
45. Vector4

Additional context

This was broken off #101.

[chapulina]

We're moving all the SWIG files that we had working for Python to the Ruby directory in #354, but we're not enabling them.

Now the work on this issue should consist of:

1. Adding each file to:

   https://github.com/ignitionrobotics/ign-math/blob/5fa6f7858a873448c9fa09be23dafc99f0f8863d/src/ruby/CMakeLists.txt#L16-L23

2. Porting the existing test from C++ / Python to Ruby

3. Making any necessary adjustments to the SWIG file

[azeey]

I would be in favor of abandoning Ruby in favor of Python.