new option to set the horizontal alignment relative to the input

[dankolz]

fixes https://github.com/bevacqua/rome/issues/150

[JosephSilber]

Any plans for this @bevacqua?

For elements that hug the right side of the screen, you simply cannot currently use Rome.

The same applies to vertical positioning. It is currently impossible to use Rome on an element that sits at the bottom of the page.