Fix for #18 along with other tweaks.

I would also like to note that in the original material design, individual elements have their own special ripple properties, e.g. the blue button receives `background-color: #2a56c6` as well, not just having an opacity applied to it. This could perhaps be something to be worked on in the future.
as noted before, ripples.js **must** allow multiple ripples on the same element, if you remove the old ones only one ripple will be visible at time.