How to do a bezier interpolation mode animation along a path?

When I parent an object to follow a path and animate it, I only get a linear mode animation and changing that in Grapth Editor to bezier doesn't work! How to do that?

• Related - blender.stackexchange.com/questions/31578/…. There actually is another way with adding several Envelope F-Modifiers in the N panel of Graph Editor. But it's very hard to setup, especially when there're a lot of points Aug 12 '15 at 21:52