Performance suggestions

[fabiosantoscode]

Hello!

I was reviewing a React component from a colleague of mine, which uses this project as a library. Everything looked wonderful on both sides, but I did a tiny performance test using firefox's performance tools with object allocation statistics turned on. You know, just for fun.

In the meantime I found some extra allocations, some of which could be very, very easily avoided! This should prevent the garbage collector from butting in and causing jank in your otherwise very smooth scroll experience.

Here are my notes, if you're interested :)

https://github.com/economist-components/component-carousel/pull/2#issuecomment-219979022

Cheers!