Slider as Nav For

New feature to set slider as nav for other slider
Fix index html indent
Add sync exemple
Merge pull request #1 from SirKnightDragoon/asNavFor

As nav for
Merge pull request #2 from kenwheeler/master

Adding multiple vertical slides feature
Fix sync and add new feature focusOnSelect option.

Fix sync of the as nav for
Fix focusOnSelect

missing parseInt on Str index
Merge pull request #3 from kenwheeler/master

Uptate to last commit
Fix index NaN speed click
Fix code indent
Add missing option focusOnSelect exemple
Add compatibility focusOnSelect

Multiple slides compatibility
Add and remove slider
Add Settings and Methods
Merge pull request #4 from kenwheeler/master

Merge
Merge pull request #5 from kenwheeler/master

Update
Merge pull request #6 from kenwheeler/master

Update
Update slick.js

Add appendArrows option.
Add an onLoadImages function

Allows customizing how images are lazy loaded. Left the default
'img[data-lazy]' way untouched.

Includes an option 'onLoadImages' which defaults to null.
Update README - appendArrows
Update index.html - appendArrow documentation