Adds evt handlers to add/remove `.x-item-pressed`

When a user taps anywhere within `.accordion-section`, we add event
listeners for `touchstart` and `touchend` that will add and remove the
`.x-item-pressed` class from `.accordion-section`, respectively.
tweak event syntax and make pressedCls a config
Set event handler on accordion header only
Merge pull request #1 from JarvusInnovations/add_class_while_pressed

Adds event handlers to add/remove `.x-item-pressed` from `.accordion-section` on touchstart/end