Make body sortable
New polymorphed element `tomalec-sortable-body`.

Inherits from `tomalec-sortable-list` but is still bit messy.
Merge branch 'master' into sortable-body
New `tomalec-sortable-body` element to apply sortable features on root level
Examples' CSS update
Fix dropping in same order
Merge branch 'master' into gh-pages