How fast can and do gravitational waves travel? I was thrilled by the recent announcement of the detection of gravitational waves. The media has done a great job explaining them and the theory behind them and I get the concept fairly well.

But if it's a warping of spacetime, not a particle phenomenon,  (or is it somehow?) How fast do these waves travel through space? Is it  constant or variable? Slower than the speed of light or even faster? If spacetime has no resistance per se, the what would keep them from traveling infinitely fast?

I'd love to understand it better and hope my question makes sense.
Gravitational waves travel at the same speed as the speed of light in a vacuum, in general relativity. In special relativity, this is the maximum speed for any interaction in nature.


If gravity was faster than the speed of light, then predictions we make according to the bending of light would be incorrect. 
If gravity was faster than the speed of light, then the orbits and positions of the planets would be completely different.


Those are my two main points, to help me prove to you that gravity travels at the speed of light.

Also, light is not the only thing in the universe which travels at the speed of light. It is about all massless particles! Photons and gluons are two good examples I can think of of massless particles, I'm not sure about gravitons though - but I'll still include them.