Basic implementation of the FlipBox class

FlipBox acts as a DOM renderer for the animation. It creates the
element structure, needed. Provides the basic API of setting the sprite
sheet and it's position for a certain frame.
Allow undefined variables in FlipBox.setFrame

Allow passing of undefined offsetX and offsetY variables in
FlipBox.setFrame method for when the offset/registration point is not
defined and isn't required.
Merge branch 'feature/flipbox' into develop