Add all methods to flickity service

[benjamincharity]

http://flickity.metafizzy.co/api.html

• Methods
  • [x] select
  • [x] previous
  • [x] next
  • [x] resize
  • [x] reposition
  • [x] prepend
  • [x] append
  • [x] insert
  • [x] remove
  • [x] destroy
  • [x] reloadCells
  • [x] getCellElements
  • [x] Flickity.data()
  • [x] selectedIndex
  • [x] selectedElement
  • [x] cells