Body nesting V2

[rcpeters]

After testing in the wild the first version of was causing issues. This version will:

• if the contentEl is type body create a new div
• append all the body children into the new div
• append the new div to the body
• ressagin contentEl(body) to be the new div

[rcpeters]

I think a better pattern would to allow a function to be passed into the config. That way no old behavior is broken but 3rd parties can easily customize. Happy refactor if that sounds good.