Index - Usage Notes

Updated the usage notes to explain what I refer to as the `bubble
button`, which appears when the page becomes relatively narrow in width.
init.js - IIFE

Placed the `$.fn.bubbleBtn` block of codes in an Immediately-Invoked
Function Expression (IIFE).
Removed ie7-pseudo

Removed ie7-pseudo in favour of a `$.pseudofy()` function that only
creates and adds in the pseudo-element when you specifically call for
it.