Allow multiple additional classes

This release allows adding multiple classes to PaginateLinks by using an array of class names. For example:

<paginate-links
  for="languages"
  :simple="{
    prev: 'Back',
    next: 'Next'
  }"
  :classes="{
    '.prev > a': ['first-class', 'second-class'] // multiple classes
  }"
></paginate-links>