Because from iframes, like Instagram embeds, have a non-responsive
element (header + footer) as well as the responsive part (the image), it
would be helpful to be able to specify the two separately. This adds an
additional data-element (data-height-adjust) which can be specified on
the .shortcake-bakery-responsive element. If this is set, that portion
of the height will be considered "static" and will not be recalculated
on resize.

Try to match the padding from the wrapper div in the initial embed code,
and use it to set the "ratio" on the shortcode. Leaves the "ratio"
argument out if it's 100%.

Satisfies minimum requirements for wp-coding-standards @Dev-Master.

Mostly whitespace cleanup and the like...

tfw phpcs has two conflicting rules applied to one line...