Update main.js

This is a size improvement over repeated document.querySelector calls, aiming to better shrink once passed through minifiers.
The script is small already but being a base reference, why not smaller, if it's possible keeping it clean?
Sorry I didn't mean to be rude but that didn't come out so well but my point is: what do you gain/win using a method that will brake when you can have exact same functionality without breaking? Do you _have to_ avoid supporting decent/relatively modern browsers with this very basic snippet or you can deal with something that will work with IE9, Safari Mobile 5.1, and older Android too?

You win nothing using `bind` there: no performance gain, no minifier gain, and you drop support with older browser that might work here too, although you might need to shim DOM4 classList, but that's different from needing to shim both DOM4 and ES 5.1

Distinct problems that should be left as distinct here. For DOM4 though, I'd actually suggest [this snippet](https://github.com/WebReflection/dom4#dom4) as optional solution for compatibility.

Sorry but I don't see my stubborn part … this project states it works with those targets, but other browsers might work too.

No need to cut them out because of `.bind` that brings nothing in this very specific snippet.

That being said, I have to rebase and receive confirmation I can sign something ^_^