Remove Hardcoded Classnames (eg, .clearfix)

[EnigmaSolved]

As I indicated elsewhere (#64), I'm a fan of keeping the plugin really light-weight. So things like the hardcoded .clearfix class being applied are undesirable. I'd much prefer that you leave that out, and let the user define their own styles based on either the default classnames (or custom classnames, when that becomes possible, eg, #138, #131).

I'd be happy to do a Pull Request if you're agreeable to this change.

Thanks for your consideration! :)