Ray-line picking : the return

Following the issues discussed here https://github.com/mrdoob/three.js/pull/3629 :

1,2,3. I changed the Ray class so that it is now used as a ray and not a line.
    I don't really know how much of an impact it could have... so it's up to you
    But I agree that there's a kind of confusion between ray/line/segment (on top of that Line in three.js is an Object3D and not a math thing...)
4. Added a few unit test for the ray
5. webgl_interactives_lines changed to canvas_interactives_lines
6. I don't think that setting the initial threshold to 1 is good.
    Depending on the scene scale, you are likely to pick every lines or none of them...

As I said previously, to get an 'absolute' threshold.. you'll have to unproject the vertices on display and compare with the mouse position or use color-picking :D