Rotates the array left the specified number of times.
This is useful if trying to create a circular queue.
@param {Array} a The Array object to operate on.
@param {Number=} [amount=1] The number of times to rotate the array left.
@return {Array<*>} The current array, rotated left.
@function
function rotateLeft (a, amount) {
                    if(!(a instanceof Array)) return a;
                    return libs.array.rotate(a, 'left', amount);
                }