getTab (span) {
    const el = document.createElement('li')
    el.classList.add('tab')
    el.style = el.style || {}
    this.applyStyles(el,
      {
        width: '100%',
        textAlign: 'left',
        lineHeight: '24px',
        height: '24px',
        fontSize: '14px',
        cursor: 'pointer'
      }
    )
    el.appendChild(span)
    return el
  }
Gets a single tab element.

@param {HTMLElement} span The tab's content.
@returns {HTMLElement} The tab element.
@see https://github.com/Dogfalo/materialize/issues/2542#issuecomment-233458602