Add styles and sample markup for the card with author details
Hide the author card initially
Inline three functions which return a fixed CSS class name
Remove unused class 'tile-box'
Complete implementation of showElement / hideElement

The implementation is based on two new utility methods, addClass()
and removeClass(), which respectively add and remove one CSS class
from an element, using HTML5 classList property if available, or
falling back to a string manipulation of the className property.
Show / hide author card when over / out of a tile
Revert unwanted changes introduced in markup together with the card

Revert "Add styles and sample markup for the card with author details"
This reverts partially commit ab3746376e782b6ab0aa38d7ed3e597f783ef3e7.

Conflicts:
	index.html