Add support for inline, non-flat support.

[brjpeters]

We currently use the color picker in an element that is fixed position as you scroll. This works great unless the color picker is open. When the color picker is open, the color picker scrolls with the page which causes a bad user experience.

This is caused by the color picker being appended to document.body instead of the element. I noticed the flat option causes the color picker to be appended to the element instead of document.body, but we don't want to have the color pickers open all the time; we are looking for the default behavior.

It would be great if you could make the color picker work with either a container option to append to instead of document.body, or make an inline option that appends the color picker to the element and makes it work like the default color picker behavior.`