Expanding documentation for api/object/LineSegments

[JonLim]

I had been wrestling with a problem for a few days regarding how to draw only certain lines when creating a line, and the documentation was not entirely clear about how THREE.LineSegments really differed from THREE.Line, nor were there decent examples of this after extensive googling.

Finally found an answer after asking SO: http://stackoverflow.com/questions/35759623/removing-linesegments-from-line

And now we're good!

As such, I've updated the docs for THREE.LineSegments to be at least a little more clear with how line segments are assembled in Three.js. Very small and simple change, but I think it was necessary for clarity.

[mrdoob]

Thanks!