Fix comment and remove unused Trait--LineSegmentTool does not inherit from BaseTool.
Fix comment and remove unused Trait--LineSegmentTool does not inherit from BaseTool.

ContinuumIO/chaco,tommy-u/chaco,tommy-u/chaco,burnpanck/chaco,burnpanck/chaco,burnpanck/chaco,ContinuumIO/chaco,ContinuumIO/chaco,tommy-u/chaco,ContinuumIO/chaco