Address #9873 and fix #9774

* Update styling of justified nav links to be more mobile friendly
(with all four rounded corners and some margin between items)
* Add note to docs to callout bogus WebKit rendering on component and
example
Fixes #10137: correct classes on thumbnails
Add margin to thumbnails for proper spacing

Hadn't thought about this until fixes #10137, but it makes sense I
think to have margin on the bottom of thumbnails for spacing when
stacking (or using different grid tiers).
Improve upon #9937: Link and put reset column stuff to action in the grid example
Fixes #10016 and updates that rather badly formatted callout
Add missing period on customize page.
Merge pull request #10204 from premist/master

Add missing period on customize page.
Merge branch '3.0.0'

Conflicts:
	dist/css/bootstrap.css
	dist/css/bootstrap.min.css
	scss/_navs.scss